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| SQL ,PL/SQL & D2K Interview Questions [message #27446] |
Fri, 03 October 2003 03:43  |
Gurusubramanyam
Messages: 79
Registered: July 2001
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1. How to implement ISNUMERIC function in SQL *Plus ?
Method 1:
Select length (translate (trim (column_name),' +-.0123456789',' ')) from dual ;
Will give you a zero if it is a number or greater than zero if not numeric (actually gives the count of non numeric characters)
Method 2:
select instr(translate('wwww',
'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ',
'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'),'X')
FROM dual;
It returns 0 if it is a number, 1 if it is not.
2. How to Select last N records from a Table?
select * from (select rownum a, CLASS_CODE,CLASS_DESC from clm)
where a > ( select (max(rownum)-10) from clm)
Here N = 10
The following query has a Problem of performance in the execution of the following query where the table ter.ter_master have 22231 records. So the results are obtained after hours.
Cursor rem_master(brepno VARCHAR2) IS
select a.* from ter.ter_master a
where NOT a.repno in (select repno from ermast) and
(brepno = 'ALL' or a.repno > brepno)
Order by a.repno
What are steps required tuning this query to improve its performance?
„Ï Have an index on TER_MASTER.REPNO and one on ERMAST.REPNO
„Ï Be sure to get familiar with EXPLAIN PLAN. This can help you determine the execution path that Oracle takes. If you are using Cost Based Optimizer mode, then be sure that your statistics on TER_MASTER are up-to-date.
„Ï Also, you can change your SQL to:
SELECT a.*
FROM ter.ter_master a
WHERE NOT EXISTS (SELECT b.repno FROM ermast b
WHERE a.repno=b.repno) AND
(a.brepno = 'ALL' or a.repno > a.brepno)
ORDER BY a.repno;
3. What is the difference between Truncate and Delete interms of Referential Integrity?
DELETE removes one or more records in a table, checking referential
Constraints (to see if there are dependent child records) and firing any
DELETE triggers. In the order you are deleting (child first then parent)
There will be no problems.
TRUNCATE removes ALL records in a table. It does not execute any triggers.
Also, it only checks for the existence (and status) of another foreign key
Pointing to the table. If one exists and is enabled, then you will get
The following error. This is true even if you do the child tables first.
ORA-02266: unique/primary keys in table referenced by enabled foreign keys
You should disable the foreign key constraints in the child tables before
issuing the TRUNCATE command, then re-enable them afterwards.
CLIENT/SERVER
What does preemptive in preemptive multitasking mean ?
Preemptive refers to the fact that each task is alloted fixed time slots and at the end of that time slot the next task is started.
What does the OLTP stands for ?
OLTP stands for On Line Transaction Processing
What is the most important requirement for OLTP ?
OLTP requires real time response.
In a client server environment, what would be the major work that the client deals with ?
The client deals with the user interface part of the system.
Why is the most of the processing done at the sever ?
To reduce the network traffic and for application sharing and implementing business rules.
What does teh term upsizing refer to ?
Applications that have outgrown their environment are re-engineered to run in a larger environment. This is upsizing.
What does one do when one is rightsizing ?
With rightsizing, one would move applications to the most appropriate server platforms.
What does the term downsizing refer to ?
A host based application is re-engineered to run in smaller or LAN based environment.
What is event trigger ?
An event trigger, a segment of code which is associated with each event and is fired when the event occurs.
Why do stored procedures reduce network traffic ?
When a stored procedure is called, only the procedure call is sent to the server and not the statements that the procedure contains.
What are the types of processes that a server runs ?
Foreground process and
Background process.
What is a event handler ?
An event handler is a routine that is written to respond to a particular event.
What is an integrity constraint ?
An integrity constraint allows the definition of certain restrictions, at the table level, on the data that is entered into a table.
What are the various uses of database triggers ?
Database triggers can be used to enforce business rules, to maintain derived values and perform value-based auditing.
What is a transaction ?
A transaction is a set of operations that begin when the first DML is issued and end when a commit or rollback is issued. BEGIN COMMIT/ROLLBACK are the boundries of a transaction.
Why are the integrity constraints preferred to database triggers ?
Because it is easier to define an integrity constraint than a database trigger.
Why is it better to use an integrity constraint to validate data in a table than to use a stored procedure ?
Because an integrity constraint is automatically checked while data is inserted into a table. A stored has to be specifically invoked.
What are the three components of a client server model ?
A Client,
A Server and
A Network/Communication software.
What are the advantages of client/server model ?
Flexibility of the system, scalability, cost saving, centralised control and implementation of business rules, increase of developers productivity, portability, improved network and resource utilization.
What are the disadvantages of the client/server model ?
Heterogeneity of the system results in reduced reliablity. May not be suitable for all applications. Managing and tuning networks becomes difficult.
What are the different topologies available for network ?
Star,
Bus,
Ring.
What is the first work of Client process ?
A client process at first establishes connection with the Server.
What are the responsibilities of a Server ?
1. Manage resources optimally across multiple clients.
2. Controlling database access and security.
3. Protecting the databse and recovering it from crashes.
4. Enforcing integrity rules globally.
In a Client/Server context, what does API (Application Programming Interface) refer to ?
An API, in a Client/Server context, is a specification of a set of functions for communication between the client and the server.
Give some examples of standard API¡¦s ?
Open Database Connectivity (ODBC),
Integrated Database Application Programming Interface (IDAPI),
XOpen
SQL/CLI
What is the main advantage of developing an application using an API ?
The application can be connected to any back end server that is supported by the API.
What is the main disadvantage of developing an application using an API ?
The application cannot use any special features of the backend server.
Why is an event driven program referred to a passive program ?
Because an event driven program is always waiting for something to happen before processing.
What are the four types of events ?
1. System Events.
2. Control Events
3. User Events
4. Other Events.
What is the difference between file server and a database server ?
A file server just transfers all the data requested by all its client and the client processes the data while a database server runs the query and sends only the query output.
What is inheritance ?
Inheritance is a method by which properties and methods of an existing object are automatically passed to any object derived from it.
What are the two components of ODBC ?
1. An ODBC manager/administrator and
2. ODBC driver.
What is the function of a ODBC manager ?
The ODBC Manager manages all the data sources that exists in the system.
What is the function of a ODBC Driver ?
The ODBC Driver allows the developer to talk to the back end database.
What description of a data source is required for ODBC ?
The name of the DBMS, the location of the source and the database dependent information.
How is a connection establised by ODBC ?
ODBC uses the description of the datasource available in the ODBC.INI file to load the required drivers to access that particular back end database.
RDBMS FUNDAMENTALS
I. INTRODUCING DATABASES :
Concept of a Database :
Traditional Approach : In this approach, independent application programs access their own independent data files. This results in many problems in data storage and retrieval.
Database Approach : In this approach, all application access a common database, which is a centralized data storage system. This approach has the following advantages :
Redundancy of data storage is reduced, Inconsistency in data is eliminated & Data sharing between applications is possible.
Interacting with a Database :
Database Management System (DBMS) : DBMS is a software that interfaces between applications and a database for all data processing activities.
Users of a DBMS : End Users, Application Programmers and Database Administrators use a DBMS, either directly or indirectly.
How users interact with a Database :
1. End users send queries to the DBMS through applications.
2. The DBMS translates the queries.
3. The DBMS retrieves data from the database.
4. The DBMS sends data to the application, which present the data to the end users.
Functions of a DBMS :
Function of DBMS Description Provided by using
Defining the data structure Defining structure of data to be stored in database Data Definition Language (DDL)
Manipulating Data Retrieving, adding, modifying, deleting data. Data Manipulation Language (DML)
Data Security Preventing unauthorized access to data. User-ids and Passwords.
Control of Data Access Allowing users to use only relevant data Data Control Language (DCL)
Architecture of a Database :
Need for an Architecture : The details about complexity and structure of data in a database in not required by end-users. Therefore, differentiating what the end-users see and what is actually there in a database is important.
Architecture of a Database : The architecture of a database comprises a set of three levels at which a database can be viewed.
External Level or View, Conceptual Level or View & Internal Level or View.
II. USING RELATIONAL DATABASE :
Basics of Relational Database :
Relational Database Management System (RDBMS) : RDBMS is the most popular form of DBMS used in the world. It uses a relational database to organize data. A relational database comprise relations, which are represented as tables.
Relation : A relation stores information about an object in the real world. A relation is represented as a table.
Attribute : Each attribute of a relation stores a piece of information about an object. Attributes are represented as columns in a tables and can be arranged in any order. Each attribute in a relation is unique and contain atomic values i.e. Atomic value contain a single value of data and Non-Atomic values contain a set of values. The number of attributes in a relation is called the degree of the relation.
Tuple : A row in a table is called a tuple of the relation. The number of tuples in a relation is known as the cardinality of the relation. Tuples in a table are unique and can be arranged in any order.
Domain : A domain is a set of valid atomic values that an attribute can take. Within a single database, an attribute cannot have different domains associated with it. A domain can include a null value, if the value for the domain is unknown or does not exist.
Identifiers for Relations :
Primary Key : An attribute that uniquely identifies a row in a table is called its primary key. A relation can have only one primary key. The primary key cannot have any null values. In case no unique key is found in a relation, two or more attributes can be treated as the primary key. Such keys are called Composite Keys.
Candidate Key : A relation can have more than one attribute that uniquely identifies a tuple. Any one of these keys can be selected as the primary key. All such attributes are called Candidate Keys. All candidate keys that are not primary keys are called Alternate Keys.
Foreign Key : An attribute that is not a candidate key is called a Nonkey. A nonkey attribute of a relation whose value matches the primary key in some other table is called Foreign Key OR is a column in a table that uniquely identifies rows from a different table.
III. INTERPRETING DATA :
Entities and Relationships :
Entity : An entity is an object that exists in the real world and is distinguishable from other objects. Each entity is represented as a table in a relational database.
Types of Entities : Entities can be classified in two ways - based on existence and based on subsets.
Based on existence, entities can be classified as Dominant and Weak entities.
Based on subsets, entities can be classifies as Supertypes and Subtypes.
Relationships : A relationship is an association between two entities.
Types of Relationships : Relationships are classified into three types based on the occurrence of the related entities.
One-to-One(1-1), One-to-Many(1-M) & Many-to-Many(M-M).
Using E/R Diagram : A E/R diagram represent entities and relationships in a database system.
Reducing E/R Diagrams to Relations :
Mapping Entities : A dominant entity is mapped to a new relation. A weak entity is mapped to a new relation. The primary key of the corresponding dominant entity is included as the foreign key in the weak entity relation.
Supertypes and subtypes are mapped to separate relations. The primary key of the supertype becomes the primary key of the subtype.
Mapping Relationships : A 1-1 relationship is mapped using a foreign key. The primary key of either of the entities is include as a foreign key in the relation of the other entity. This relationship is rare, because data elements related in this way are normally placed in the same table.
A 1-M or M-1 is mapped by introducing a foreign key. A primary key is the ¡¥one¡¦ side of the relationship, and the foreign key is the ¡¥many¡¦ side of the relationship. This relationship are most common.
A M-M involves the creation of a new relation. M-M are problematic and cannot be adequately expressed directly in a relational db. It is expressed using intersection tables. An intersection table contains two (or more) foreign keys, relating the primary key values of two (or more) tables to each other. The role of an intersection table is to convert the M-M into two 1-M relationships that can be easily handled by the database.
IV. SIMPLIFYING DATA :
Need for Simplifying Data :
Normalization : Normalization is a formal process of developing data structures in a manner that eliminates redundancy and promotes integrity. You need to simplify structure of data in relations for easy storage and retrieval. The process of simplifying relations is called normalization. The new relations that are obtained after normalization are called normalized relations.
Normalization has three well defined steps :
The relations that you get at the end of the first step are said to be in 1NF.
The relations that you get at the end of the second step are said to be in 2NF.
The relations that you get at the end of the third step are said to be in 3NF.
Simplifying Data to 1NF (Eliminate Repeating Groups) : A repeating group is a set of columns that store similar info that repeats in the same table. To simplify data to 1NF, you ensure that all attributes values in a relation have atomic values. If there are attributes in a relation with non-atomic values, move these attributes to a new relation and choose an appropriate primary key for it. E.g. SupItem Table Item field having atomic.
Simplifying Data to 2NF (Eliminate Redundant Data) :
Redundant data is data that is expressed multiple times unnecessarily, or depends only on part of a multi-valued key.
Functionally Dependent Attributes : Functionally Dependent Attributes are those that belong to a single entity or relationship and depend on its unique identifier. To simplify data to 2NF, you ensure that all nonkey attributes in a relation are functionally dependent on the whole key and not part of the key.
Conversion from 1NF to 2NF : To convert a relation in 1NF to 2NF, move all nonkey attributes that are not wholly dependent on the primary key, to a new relation. Then, choose an appropriate primary key for the new relation. E.g. Separating Sup. table and Item table.
Simplifying Data to 3NF (Eliminate Columns not Dependent on the Key) :
Columns in each table should be a group of columns in which the data in each column contributes to the description of each row in the table.
Transitively Dependent Attributes : Transitively Dependent Attributes in a relation are those that are dependent on a nonkey attribute and not the primary key. To simplify data to 3NF, you ensure that there are no attributes in a relation that are transitively dependent on other attributes.
Conversion from 2NF to 3NF : To convert a relation in 2NF to 3NF, move all transitively dependent attributes to a new relation. Then, choose an appropriate primary key for the new relation. E.g. Status is dependent on City in Sup. table, so move those two to separate table.
Simplifying Data to 4NF (Isolate Independent Multiple Relationships) :
V. STORING & RETRIEVING DATA :
Language Support for an RDBMS :
SQL :SQL is the language that provides command to interact with the data in the database. SQL consists of three components - DDL, DML & DCL.
DDL : DDL comprises commands you can use to create and modify the database structure.
DML : DML comprises commands you can use to add, modify, delete and query data in the database.
DCL : DCL comprises commands you can use to control the user access to the database.
Organizing the Database :
Base Tables : A database comprises base tables, which have the following features :
They physically exist on the disk, Each of them has a unique name & they contain data that is crucial to an organization.
Their attributes have data types such as character, integer, decimal, date and time.
CREATE TABLE : This is a DDL command in SQL that creates a new table in a database.
Syntax : CREATE TABLE table-name (column-name data-type [[size]]
NOT NULL/DEFAULT default-value]]
CHECK (column-name > 0)
UNIQUE (column-name)
PRIMARY KEY (column-name)
FOREIGN KEY (column-name) REFERENCES table-name)
ALTER TABLE : This is a DDL command in SQL that modifies the structure of an existing table.
Syntax : ALTER TABLE table-name
ADD (column-name data-type [[size]] [[NOT NULL DEFAULT]]...)
primary key definition / foreign key definition
DROP PRIMARY KEY / DROP FOREIGN KEY)
DROP TABLE : This is DDL command in SQL that deletes the an existing table. Once you delete a table, all data contained in it is lost and cannot be recovered. The storage space used by this table is also released.
Syntax : DROP TABLE table-name
Interacting with a Database :
SELECT : This is a DML command in SQL that retrieves data from the database in the form of query results. The command supports the following keywords and clauses :
FROM This keyword specifies the name of the table.
* This keyword selects all the columns of the table.
WHERE This keyword gives the search condition that specifies the data to be retrieved.
AND This operator is used to combine two or more search conditions.
ORDER BY This keyword sorts the query result on one or more columns.
GROUP BY This keyword groups the query result and lets you generate summary result for each group.
NULL values This value indicates that the data is not present.
Subquery This is the query that is place inside the main query. It passes its query result to the main query.
INSERT : This is a DML command in SQL that you use to add data in rows of a table.
SYNTAX : INSERT INTO table-name (column-names) VALUES (constant/NULL)
UPDATE : This is a DML command in SQL that you use to change data on rows of a table.
Syntax : UPDATE table-name SET column-name-value WHERE condition
DELETE : This is a DML command in SQL that removes one or more rows of data from a table.
Syntax : DELETE FROM table-name WHERE condition.
End-user's View of a Database :
Views : Views are relations that are derived from one or more source tables. Views have the following features:
Views let you restrict the access to data so that end-users see data relevant to them.
Views do not physically exist in the database and only their definition is stored by an RDBMS.
An RDBMS accesses the source tables for data to be retrieved from a view.
Any changes that users make to views do not reflect in the source tables if the view has been created using a Join condition.
Views created WITH CHECK OPTION allows for an added measure of security in a view. For example, the user will not be able to insert or update a row that could not be selected by the view-with check option prevents this from happening.
CREATE VIEW : A view can be created using the CREATE VIEW command.
Syntax : CREATE VIEW view-name (column-names) AS query.
Retrieving Data from a View : Once you create a view, you can retrieve data from it using the SELECT command, just as you do for a table.
Restricting Access to a Database :
GRANT : This is a DCL command in SQL that you use to grant a specific set of authorities to one or more users.
Syntax : GRANT (SQL command) (column-names) ON table-name TO user-name.
REVOKE : This is a DCL command in SQL that you use to take away a specific set of authorities from one or more users.
Syntax : REVOKE (SQL command) ON table-name TO user-name.
VI. ENSURING INTEGRITY OF DATA :
The concept of Data Integrity :
Data Integrity : Data Integrity refers to the correctness and completeness of data in a database.
Integrity Constraints : Integrity constraints allows only correct changes to be made to a database. There are two types of integrity constraints - entity integrity and referential integrity.
Entity Integrity : Entity Integrity ensures that for each row in a table, the value of the primary key is unique and is not null.
Referential Integrity : Referential Integrity ensures that for each row in a table, the value of the foreign key is present in the reference table.
Grouping commands related to a task :
Transaction Processing : A transaction is a sequence of one or more SQL commands that together form a logical task. Transaction Processing ensures that when the RDBMS is making changes related to a single task, either all changes are made as a unit or no changes are made.
Commit : Commit is an SQL command that indicates the successful end of a transaction. After an RDBMS executes this command all the changes are made to the database.
Rollback : Rollback is an SQL command that cancels a transaction before it is complete. The rollback command removes the changes of all previous commands in a transaction from the buffer.
Controlling Concurrent Data Access :
Concurrency Control : All RDBMS must ensure that the transactions of concurrent users do not interfere with each other. If it does not handle the transactions properly, the problems of lost update, uncommitted data, or inconsistent data might occur.
Lost Update Problem : Lost update problem occurs when an update made by a transaction is lost due to an update made by another transaction.
Uncommitted Data Problem : Uncommitted data problem occurs when a transaction accesses data that has been updated by a previous transaction that has not yet ended.
Inconsistent Data Problem : Inconsistent data problem occurs when a transaction accesses data from the database and simultaneously another transaction is changing that data.
Locking : Locking is a facility provided by an RDBMS to ensure that a transaction does not interfere with any other transaction. Locking prevents the problem of lost update, uncommitted data and inconsistent data. An RDBMS provided two types of locks for locking a part of the database - shared locks and exclusive locks.
Shared Locks : If a transaction is only reading data from a database, it gets a shared lock on that part of the database. Other transactions can also get a shared lock on that part of the database to read data. However, they cannot change the data.
Exclusive Locks : If a transaction is updating data in a database, it gets an exclusive lock on that part of the database. No other transaction can read or change this data.
Client Server Computing Model
I. Client Server Paradigm :
Introduction : In the past decade, organizations have restructured and become global. The globalization and restructuring have led to a need for distributed and flexible information access. That traditional computing paradigms like host-based and master/slave processing do not adequately address the information requirements of modern business. That the client/server model provides an architecture that harness contemporary technology to meet the computing needs of the modern business organization. Also called Distributed Application Processing or Co-Operative Application Processing
Host Based Processing - The Centralized Paradigm : Centralized computing treated applications as an integrated unit. Applications ran on a single processor. The same processor generated the user interface and manipulated data. Dumb terminals were used for data access and display. Disadvantages are : Data was centralized and often not accessible to those who needed it. The host computed did all the work, was frequently overloaded, and response times were often poor. Hardware choices and scalability were limited by proprietary architecture's. User interfaces were unfriendly, Data access was inflexible and governed by available 3GL programs.
Master/Slave - The First Distributed Computing Paradigm : As PC's and intelligent terminals became available, a limited amount of processing was transferred to the terminal. Intelligent terminals often validated data and provided editing functions. Such terminal were called Slaves. Slaves were controlled by Master computer which did the main processing and stored all data. It had one distinct advantage. It reduced the load on the main processor. However, the other problems associated with host-based processing remained.
Client/Server - A Distributed Computing Paradigm : The client/server paradigm evolved as an attempt to address the new computing needs of business and utilize new technologies.
Advantages : Client/Server makes it possible to harness the computing power available on PCs and other workstations in an organization. Response times are improved as processors are not overloaded. Hardware and software choices can be application oriented as they do not necessarily have to run on a proprietary computer. Network traffic is reduced because the processing power available at the end user terminal makes it unnecessary to send detailed instructions over the network as in the case of host based & master/slave systems. Computing power can be added in smaller units making the system easily scaleable.
Disadvantages :The inherent heterogeneity makes System Integration, Administration & Maintenance a formidable challenge.
ORACLE 7 is an exceptional RDBMS & also an excellent DB server because it supports all major OS
for both clients & servers i.e. MSDOS, Netware, Unixware, OS/2 etc. Oracle Network software SQL*NET support all major network communication protocols TCP/IP, SPX/IPS, Named Pipes & DECNET. It has got client server feature that developers can use to minimize network traffic between clients & servers. Has features that makes it easy to administer a complicated client server system.
Client/Server Approach : The client/server paradigm optimizes the use of computer resources by distributing application processing among multiple processors. The client/server model computers are classified as Clients and Servers, where Clients are requesters of services and Servers are provider of services. Typically, clients handle user interface function & server handle data management function.
Client/Server Architecture requires Processing to be distributed over more than one computing system. Client-initiated client/server interactions. Server control over the services that can be requested by the client. Servers to arbitrate between conflicting client requests. A communication system that enables clients & servers to communicate.
Multitasking can be defines as the capability of an OS to run multiple applications concurrently. A Multitasking OS allocates a certain amount of CPU time to each task. In Preemptive multitasking, the OS controls the amount of CPU time allocated to a task. In non-preemptive multitasking, the application controls the CPU time and the CPU is released only after the task is completed.
Multithreading is an extension of multitasking. It allows multitasking within an application. Programs and subroutines within a program can execute concurrently in a multithreaded environment. Several user process for a single server process.
Database Server should have preemptive multitasking & multithreading capability. Support a standard RDBMS. Support a standard Network Operating System.
Tools such as RDBMS, Application Software, Application Program Interfaces, Stored Procedures, Remote Procedure Call (RPC) & Application Development Tools are an important part of client/server systems. Such tools improve productivity and also play a role in making client/server systems more open. An API is a set of functions that translates client requests into a format that the server can understand. RPC is essentially a messaging system which allows stored procedures to be invoked. Many RPCs allows procedures to be invoked across heterogeneous platforms and also provide the required data translation services.
There are several application designs possible in the client/server model depending on how application processing is distributed.
In Distributed Presentation, the presentation function is divided between the client & the server. Useful in situations where PC or workstations are connected to mainframes. Used to enhance the user interface of mainframe based applications.
In Remote Presentation, the entire presentation part of the application resides on a different computer than the one that has the logic function. Used in applications where user interaction is completely static and predetermined.
In Distributed Logic, the logic function is placed on more than one platform thus, improving response time by allowing the logic to execute simultaneously on several processors.
In Remote Data Management, the application logic resides on different computer than the one that has the data and the DBMS. Easy to implement and often provide end-users with totally transparent access to data.
In Distributed Data Management, the data and DBMS is distributed among multiple nodes and distribution of application logic.
Goals of Client/Server Paradigm is the end-user. Client/Server seeks to provide end-user transparent access to the computing resources of the organization. The goal is referred to as single system image. There are four attributes of single system image :
Location Transparency : Users must be able to access data without knowing the location of the data. Users should not have to learn & use different commands for accessing data from different locations.
Interoperability requires that applications and processing tasks be freely portable across heterogeneous computing resources.
Consistent User Interfaces require that applications retain the same user interface across heterogeneous computing platforms. Common computing tasks are represented consistently across applications.
Enterprise-wide Resource Sharing is the common thread that links all of an enterprise's computing resource
II. Concepts for Client/Server :
Introduction : RDBMS's standardize data storage and access and are therefore ideal for implementing client/server systems. The physical structure of a network is called Network Topology i.e. refers to the way the cabling of a network is physically structured. The rules that govern the process of data transmission in a network are collectively referred to as Network Protocol. Graphical User Interfaces improve productivity because they reduce learning time
and are easier to use.
Distributed Database Support : The capability of an RDBMS to manage databases lying at more than one location. To provide distributed database support, an RDBMS must be able to provide transparent access to data, Join tables on different platforms, Handle and manage distributed queries and Ensure that transactions are successfully completed on all relevant databases.
Network : Network has six basic functions, Naming, Segmentation, Segmenting, Flow Control, Synchronization, Priority & Error Control. There are three types of network topologies, Bus, Star & Ring. There are three types of transmission media, Twisted Pair, Coaxial Cable & Optic Fibre. There are three types of data transmission methods, Centralized, Distributed & Random.
GUIs : GUI must support mouse events, keyboard events, menu events, resizing events, activation/deactivation events and initialize/terminate events. GUI should be portable, should support wide variety of development tools & be an industry standard.
III. Client/Server Software :
Back-end Software : It is made up of Database Servers & Network Operating Systems. The database server manages data on the system & maintains data integrity. Database server requires some special features. Compatibility i.e. must be able to work on different operating systems. SQL Implementation i.e. must support standard ANSI SQL since it can communicate with different SQL dialects. Stored Procedures i.e. must be able to use SP as they are analyzed, compiled and optimized. Referential Integrity i.e. allows the server to synchronize change to columns that are part of multiple tables. Declarative RI establishes precise rules for use of columns that are common across tables. Built into db software and enforced by default. In Procedural RI, each db command is associated with a trigger. When command is issued, the trigger sets of a series of commands that make the necessary changes. Disadvantage is programmers must write triggers leading to errors. Multithreading i.e. support execution of multiple tasks simultaneously. Distributed Database Support i.e. able to divide database tasks among multiple CPUs. Also, able to join tables located on different servers, & manage SQL queries sent to different servers. Concurrency Control i.e. support automatic escalation, the server locks a record, if a single record is being modified. A page, if several records are being modified. A table, if several pages are being modified. Transaction Control i.e. protect transactions from system failures. In two phase commit, all workstations are notified of database changes, and if system fails, all sites rollback.
NOS controls the transmission of data across the network and manages the sharing of hardware and software resource on the network. Four important features are Operating Environment Support, Workstation Support, Security & Protocol Support.
Development Tools are made up of SQL/3GL programming tools & Front-end development tools.
End User Tools are made up of Decision Support Tools and PC-based add-ons.
IV. Migrating to Client/Server :
Evaluating the Client/Server Option : To evaluate the following before deciding on client/server. Application requirements, Geographical requirements & Productivity Gains. Client/Server is most suitable for applications are decision support or on-line transaction processing (OLTP). The distances are site or city & both developer & end-user productivity are expected to increase.
Planning for Migration : Planning is needed to reduce problems with network load, training & systems maintenance. Migration plan must include analysis, selection, prototyping & implementation as activities. Planning must include end-users, developers and system administrators as resources. To specify system requirements for end-users, developers, system managers and the business as a whole. To evaluate business priorities to eliminate stagnation & disruption.
Implementing Client/Server : The Systems Integration Life Cycle (SILC) is made up of preparation, detailing and execution. Managing SILC projects involves planning, controlling & completing. System maintenance involves ensures reliability, ensuring serviceability and monitoring performance. The training must cover end-users, developers & system administrators.
ORACLE
I. SQL*PLUS :
SQL is an English like language consisting of commands to store, retrieve, maintain & regulate access to your database.
SQL*PLUS is an application that recognizes & executes SQL commands & specialized SQL*Plus commands that can customize reports, provide help & edit facility & maintain system variables.
NVL : Null value function converts a null value to a non-null value for the purpose of evaluating an expression.
Numeric Functions accept numeric I/P & return numeric values. They are MOD, SQRT, ROUND, TRUNC & POWER.
Date Functions are ADD_MONTHS, LAST_DAY, NEXT_DAY, MONTHS_BETWEEN & SYSDATE.
Character Functions are INITCAP, UPPER, LOWER, SUBSTR & LENGTH. Additional functions are GREATEST & LEAST.
Group Functions returns results based upon groups of rows rather than one result per row, use group functions. They are AVG, COUNT, MAX, MIN & SUM.
TTITLE & BTITLE are commands to control report headings & footers.
COLUMN command define column headings & format data values.
BREAK command clarify reports by suppressing repeated values, skipping lines & allowing for controlled break points.
COMPUTE command control computations on subsets created by the BREAK command.
SET command changes the system variables affecting the report environment.
SPOOL command creates a print file of the report.
JOIN is the form of SELECT command that combines info from two or more tables.
Types of Joins are Simple (Equijoin & Non-Equijoin), Outer & Self join.
Equijoin returns rows from two or more tables joined together based upon a equality condition in the WHERE clause.
Non-Equijoin returns rows from two or more tables based upon a relationship other than the equality condition in the WHERE clause.
Outer Join combines two or more tables returning those rows from one table that have no direct match in the other table.
Self Join joins a table to itself as though it were two separate tables.
Set Operators supported by Oracle are :
Union is the product of two or more tables.
Intersect is the product of two tables listing only the matching rows.
Minus is the product of two tables listing only the non-matching rows.
Correlated Subquery is a subquery that is evaluated once for each row processed by the parent statement. Parent statement can be Select, Update or Delete. Use CRSQ to answer multipart questions whose answer depends on the value in each row processed by parent statement.
Multiple columns can be returned from a Nested Subquery.
Sequences are used for generating sequence numbers without any overhead of locking. Drawback is that after generating a sequence number if the transaction is rolled back, then that sequence number is lost.
Synonyms is the alias name for table, views, sequences & procedures and are created for reasons of Security and Convenience. Two levels are Public - created by DBA & accessible to all the users. Private - Accessible to creator only. Advantages are referencing without specifying the owner and Flexibility to customize a more meaningful naming convention.
Indexes are optional structures associated with tables used to speed query execution and/or guarantee uniqueness. Create an index if there are frequent retrieval of fewer than 10-15% of the rows in a large table and columns are referenced frequently in the WHERE clause. Implied tradeoff is query speed vs. update speed. Oracle automatically update indexes. Concatenated index max. is 16 columns.
Data types :
Max. columns in a table is 255. Max. Char size is 255, Long is 64K & Number is 38 digits.
Cannot Query on a long column.
Char, Varchar2 Max. size is 2000 & default is 1 byte.
Number(p,s) p is precision range 1 to 38, s is scale -84 to 127.
Long Character data of variable length upto 2GB.
Date Range from Jan 4712 BC to Dec 4712 AD.
Raw Stores Binary data (Graphics Image & Digitized Sound). Max. is 255 bytes.
Mslabel Binary format of an OS label. Used primarily with Trusted Oracle.
Order of SQL statement execution : Where clause, Group By clause, Having clause, Order By clause & Select.
Transaction is defined as all changes made to the database between successive commits.
Commit is an event that attempts to make data in the database identical to the data in the form. It involves writing or posting data to the database and committing data to the database. Forms check the validity of the data in fields and records during a commit. Validity check are uniqueness, consistency and db restrictions.
Posting is an event that writes Inserts, Updates & Deletes in the forms to the database but not committing these transactions to the database.
Rollback causes work in the current transaction to be undone.
Savepoint is a point within a particular transaction to which you may rollback without rolling back the entire transaction.
Set Transaction is to establish properties for the current transaction.
Locking are mechanisms intended to prevent destructive interaction between users accessing data. Locks are used to achieve
Consistency : Assures users that the data they are changing or viewing is not changed until the are thro' with it.
Integrity : Assures database data and structures reflects all changes made to them in the correct sequence.
Locks ensure data integrity and maximum concurrent access to data. Commit statement releases all locks. Types of locks are given below.
Data Locks protects data i.e. Table or Row lock.
Dictionary Locks protects the structure of database object i.e. ensures table's structure does not change for the duration of the transaction.
Internal Locks & Latches protects the internal database structures. They are automatic.
Exclusive Lock allows queries on locked table but no other activity is allowed.
Share Lock allows concurrent queries but prohibits updates to the locked tables.
Row Share allows concurrent access to the locked table but prohibits for a exclusive table lock.
Row Exclusive same as Row Share but prohibits locking in shared mode.
Shared Row Exclusive locks the whole table and allows users to look at rows in the table but prohibit others from locking the table in share or updating them.
Share Update are synonymous with Row Share.
Deadlock is a unique situation in a multi user system that causes two or more users to wait indefinitely for a locked resource. First user needs a resource locked by the second user and the second user needs a resource locked by the first user. To avoid dead locks, avoid using exclusive table lock and if using, use it in the same sequence and use Commit frequently to release locks.
Mutating Table is a table that is currently being modified by an Insert, Update or Delete statement.
Constraining Table is a table that a triggering statement might need to read either directly for a SQL statement or indirectly for a declarative Referential Integrity constraints.
Pseudo Columns behaves like a column in a table but are not actually stored in the table. E.g. Currval, Nextval, Rowid, Rownum, Level etc.
SQL*Loader is a product for moving data in external files into tables in an Oracle database. To load data from external files into an Oracle database, two types of input must be provided to SQL*Loader : the data itself and the control file. The control file describes the data to be loaded. It describes the Names and format of the data files, Specifications for loading data and the Data to be loaded (optional). Invoking the loader sqlload username/password controlfilename <options>
PL/SQL :
Data types are NUMBER, CHAR/VARCHAR2, DATE & BOOLEAN.
Arrays are not allowed & only one identifier per line is allowed.
Attributes of PL/SQL objects are %TYPE, %ROWTYPE.
PL/SQL Block is a standard PL/SQL code segment. Block consists of three parts.
Declarative Section for variables, constants & exceptions. This section is optional.
Executable Section which is mandatory.
Exception Handlers which is optional.
PL/SQL supports only DML i.e. INSERT, UPDATE, DELETE & SELECT...INTO.
SQL Functions can be referenced within a SQL statement i.e. Numeric (SQRT,ROUND,POWER),
Character (LENGTH,UPPER), DATE (ADD_MONTHS,MONTHS_BETWEEN) &
Group (AVG,MAX,COUNT). Most SQL functions are available outside SQL statement except for group functions.
Code Simple Loops repeats a sequence of statements multiple times.
Syntax : LOOP
<Sequence of Statements>
END LOOP;
Code Numeric FOR Loops repeat a sequence of statements a fixed number of times.
Syntax : FOR <index> IN [[ REVERSE ]] <integer>..<integer> LOOP
<sequence of statements>
END LOOP;
<index> is implicitly of type number. Defined only within the loop & Value can be referenced in an expression, but a new value cannot be assigned to the index within the loop.
Code While Loops repeats a sequence of statements until a specific condition is no longer TRUE.
Syntax : WHILE <condition> LOOP
<sequence of statements>
END LOOP;
<condition> can be any legal PL/SQL condition & statements will be repeated as long as condition evaluates to TRUE.
Code GOTO Statements jumps to a different place in the PL/SQL block.
Syntax : GOTO label_name;
Legally use a GOTO a statement that is in the same sequence of statements as the GOTO.
In the sequence of statements that encloses the GOTO statement (outer block).
Labels can label any statement. Used as targets for GOTO statements, use labels for blocks and loops, Label a block to allow referencing of DECLAREd objects that would otherwise not be visible because of scoping rules, Label a block to allow a variable to be referenced that might be hidden by a column name, Label a loop to allow an object to be reference that would otherwise not be visible because of scoping rules & Label an EXIT as a convenient way to specify exits from outer loops.
Cursors are associated with every SQL DML statement processed by PL/SQL. Two types are Explicit i.e. Multiple row SELECT statements & Implicit i.e. INSERT, UPDATE, DELETE & SELECT...INTO statements. Implicit cursor is called the SQL cursor-it stores info concerning the processing of the last SQL statement not associated with an explicit cursor. OPEN, FETCH & CLOSE do not apply. All cursor attributes apply.
Cursor has to be explicitly defined when a query returns multiple rows to process beyond the first row returned by the query & to keep track of which row is currently being processed.
Declare the cursor to associate its name with a SELECT statement.
Syntax : DECLARE
CURSOR <cursor_name>
IS <regular_select_statement>;
Open the cursor to process the SELECT statement and store the returned rows in the cursor.
Syntax : OPEN <cursor_name>;
Fetch data from the cursor and store it in specified variables.
Syntax : FETCH <cursor_name> INTO <var1, var2...>;
Close the cursor to free up resources. Cursors must be closed before they can be reopened.
Syntax : CLOSE <cursor_name>
Explicit Cursor Attributes are %NOTFOUND, %FOUND, %ROWCOUNT & %ISOPEN.
Reference the current cursor row with the WHERE CURRENT OF statement. The cursor must be declared with a FOR UPDATE OF clause.
Syntax : WHERE CURRENT OF <cursor_name>
Reference Cursors FOR Loops to specify a sequence of statements to be repeated once for each row that is returned by the cursor with the Cursor FOR Loop.
Syntax : FOR <record_name> IN <cursor_name> LOOP
--statements to be repeated go here
END LOOP;
Cursor FOR loops (CFL) are similar to Numeric For Loops(NFL). CFL specify a set of rows from a table using the cursor's name. NFL specify an integer range. CFL record takes on vales of each row. NFL index takes on each value in the range. Record_name is implicitly declared as
record_name cursor_name%ROWTYPE
When a CFL is initiated, an implicit OPEN cursor_name is initiated.
For each row that satisfies the query associated with the cursor, an implicit FETCH is executed into the components of record_name.
When there are no more rows left to FETCH, an implicit CLOSE cursor_name is executed and the loop is exited.
Declare cursors to use parameters
Syntax : DECLARE
CURSOR <cursor_name> [[(param_name param_type)]]
IS <regular select statement>;
Exception Handlers : In PL/SQL, errors are called exceptions. When an exception is raised, processing jumps to the exception handlers. An exception handler is a sequence of statements to be processed when a certain exception occurs. When an exception handler is complete, processing of the block terminates. Two types are Predefined Internal Exceptions which corresponds to approximately 20 common ORACLE errors & Raised automatically by PL/SQL in response to an ORACLE error.
Eg.too_many_rows,no_data_found,invalid_cursor,value_errori.e. arithmetic,numeric,string,conversion or constraint error occurred, zero_divide, dup_val_on_index,cursor_already_open etc.
User-Defined Exceptions must be declared & must be RAISEd explicitly.
Only one handler per block may be active at a time & If an exception is raised in a handler, the search for a handler for the new exception begins in the enclosing block of the current block.
Exception-Init : Exceptions may only be handled by name not ORACLE error number. So, name an ORACLE error so that a handler can be provided specifically for that error.
Syntax : PRAGMA EXCEPTION_INIT (<user_defined_exception_name>, <ORACLE_error_number>);
SQLCODE & SQLERRM provides info on the exception currently being handled & especially useful in the OTHERS handler.
SQLCODE returns the ORACLE error number of the exception, or 1 if it was a user-defined exception.
SQLERRM returns the ORACLE error message associated with the current value of SQLCODE & can also use any ORACLE error number as an argument.
SQLCODE & SQLERRM cannot be used within a SQL statement. If no exception is active SQLCODE = 0 & SQLERRM = 'normal, successful completion'.
SQL*FORMS :
Form is a tool for developing and executing forms based interactive applications that can access info from ORACLE database.
Blocks describes each section or subsection of the form and serves as the basis of default database interaction.
Fields represents columns or data entry areas and describes how data should be displayed and validated and how an operator should interact with the data while it is entered.
Pages is a collection of display info such as constant texts and graphics. All fields have to be displayed on some page.
Pop-Up Pages Non-Pop-Up Pages
Appear in windows Overlay the entire screen
Created by selecting pop-up page attribute Default type of page
Can be larger or smaller than the screen Can only be the size of the screen
Can appear anywhere on the screen Must be positioned at the upper left hand corner of the screen
Can be a section (view) of a page Must fill the entire text region
Many pages can appear on the screen at one time Only one non-pop-up page can appear on the screen
Page Size specifies the size of the pop-up page.
View Size specifies the size of the view that appears on the screen i.e. how much of the pop-up is shown.
View Location specifies where on the screen the view of the pop-up page appears; the X and Y coordinates of the screen define the upper left corner of the view.
View Page specifies the initial location of the view on the page, i.e. the part of the pop-up page that is shown; the X & Y coordinates of the page define the upper left corner of the view.
Screen Painter is used to edit screen images, add constant text and graphic elements.
Zoom In : Displays the form or spread table for the objects that are owned by the current object.
Zoom Out : Displays the form or spread table for the object that owns the current object.
Validation Unit is a characteristic which determines the max. amount to data to be entered before form initiates validation. It corresponds to a unit of data which can be field, record, block or form.
Navigation is performed to move the cursor from one location to another.
Cursor is an instance of field, outside the form or undefined.
Row Id is a column created by ORACLE when a table is created. It contains a value for each row which uniquely identifies that row. When a block is created, forms add a non-displayable, non-up dateable field named row id. Forms uses row id to determine what rows to fetch from db or reserve in db and what rows to update or delete during posting. It helps forms to manage transactions and is used to update a table that is not associated with a block in the form.
Trigger is a piece of PL/SQL code that is executed or triggered by an event while the form is running. It validates data entry, performs calculations, control the flow of application & replace or enhance default processing.
Trigger Point is a temporal space in an event with which a specific trigger type is associated.
Types of Triggers : Most key triggers are function key triggers; they have a one-to-one relationship with specific keys.
Function Key Triggers : Fires when a particular Forms function key is pressed.
Replace or supplement default function key functionality, Perform multiple or complex functions & Disable function keys.
Key Startup : Fires at the end of the entering the form event. Considered as key trigger because its action is similar to an operator pressing a startup function key.
Set up form default, Send a message to the operator as soon as the form comes up on the screen & Perform an automatic query upon entering the form.
Key Others : Associate a key-others trigger with all keys that can have key triggers associated with them but are not currently defined by a function key triggers.
Key Fn : Attach key-Fn triggers to any one of ten key sequences that normally do not perform any SQL*Form operations. Before attaching key triggers to these keys, run Oracle*Terminal to map the keys to the appropriate functions.
Navigational Triggers : Fires when entering or leaving a form, block, record or field.
Restrict access to a form, Print messages, Derive a complex default value, Keep a running total & Perform calculations.
Validation Triggers : Validation is an internal process by which Forms determines whether the data in an object is correct. Validation triggers fire when validation is performed. Validation occurs when the operator has entered or changed data in an object and then tries to leave the object. Validation does not occur when the operator is in Enter Query mode. Validation or Navigation triggers cannot contain Restricted Packaged Procedures.
Fires as last part of field validation, Changes, Calculates & Validates a field value.
Query Triggers : Fires when entering & executing a query, and when counting query hits. Defined only at the block or form level. Pre-Query fires once before block is queried. Post-Query fires once for every record fetched by the query.
Error & Message Handling Triggers : Write these triggers to replace the default SQL*Forms error or informative messages. On-Error & On-Message trigger fires when Forms displays an error or an informative message respectively.
Trap & recover from an error, Replace a standard message with a custom message.
Transactional Triggers : Fires during commit processing - an event that makes the data in the database identical to the data in the form.
Sets up special locking requirements, Update an audit trial, Prevent Insert/Update/Delete actions & Modify Insert/Update/Delete actions.
Packaged Procedure is a predefined piece of PL/SQL procedure that executes a SQL*Forms function.
Restricted Packaged Procedure is any packaged procedure that affects the basic functions of SQL forms. It is used only in Key triggers, user named triggers that are invoked by key triggers & On-New-Field-Instance trigger.
Do_Key packaged procedure executes the key trigger that corresponds to the specified packaged procedure. If no such trigger executes, then the specified packaged procedure executes. This behavior is analogous to the user pressing the corresponding function key.
Syntax : DO-KEY (package procedure name)
Packaged Function is a predefined piece of PL/SQL function that evaluates some aspect of the current SQL*Forms session and returns a value.
Name_In packaged function returns the contents of the variable to which you apply it. Returned value is in the form of character string. Also use Name_In to return number and dates as character strings and then convert those strings to the appropriate data types.
Call packaged procedure runs an indicated form while keeping the parent form active. SQL form runs the called form with the same options as the parent form. When called form is exited thro' the EXIT function or as a result of navigational failure, processing resumes in parent form at the point where the call occurred.
Call_Form runs an indicated form while keeping the parent form active.
Open_Form opens an indicated form to create multiple form application called form is modal.
New_Form exits the current form and enters the indicated form.
Key-Duprec trigger copies the values of each field in the record with the next lower sequence number to the corresponding fields in the current record. The current record must not correspond already to a row in the database. If it does, an error occurs and calls the Duplicate_Record packaged procedure.
Primary Key Field Attributes indicates that the field is a unique characteristics for a record or part of unique key. To ensure that an inserted record or updated record does not duplicate an existing record, give the critical field the primary key characteristics and give the block the primary key characteristics.
Anonymous Block is a PL/SQL block without a name and this block can be executed from the trigger in which it is defined. It does not require BEGIN & END keywords. It has to be included if it has Declaration section.
Form Level Procedure are callable PL/SQL blocks. The full PL/SQL syntax, including declarations and keywords BEGIN & END are required. They cannot contain anonymous block. These procedures can use any command that a trigger can use. They can also take arguments and return values, just as subroutines do in 3GL. It can be called from other procedures & triggers. Advantages are
Reduce the amount of logic the designer needs to write for any task, Leads to more efficient & consistent applications, Can be called by another procedure or trigger & Can pass parameters.
User Exits is a subroutine which is written and linked into SQL forms executable files. It is a link to pass data from forms to host language programs and receives the result. It performs complex data manipulation, pass data to forms from OS files, manipulate long raw data, support PL/SQL blocks and control real time devices such as printer or robot. It returns a integer value which indicates Success, Failure or Fatal Error.
Types :
Oracle PreCompiler User Exits : Incorporates Oracle Precompiler interface. Allow to write a subroutine using one of the following host language & embedded SQL commands. Host language are ADA, C, COBOL, FORTRAN, PASCAL & PL/1. With embedded SQL commands, an Oracle Precompiler user exit can access oracle databases. Also access SQL*Forms variables & fields. Because of this feature, most of user exits is Oracle Precompiler user exits.
Oracle Call Interface User Exits : Incorporates Oracle Call Interface. Allows to write a subroutine that contains call to Oracle database but cannot access SQL*Forms variable & fields.
Non-Oracle User Exits : Does not incorporate either precompiler interface or OCI. Non-Oracle user exit might be entirely written using C. Cannot access Oracle database & SQL*Forms variable & fields.
PL/SQL Variable is a local variable that is active only within the anonymous block or form level procedure in which it has been declared.
Global Variable is a forms variable that is active in any trigger within a form and is active through out the session. Stores a character string of upto 255 characters long. Before a variable is active, it should be initialized thro' a trigger or it will be initialized first time you assign a value to it. Delete any variable with ERASE package procedure. Global variable declared in one form can be used in called form. Used to store data values that should not be stored inside a block or you want to share between forms during form session.
Syntax : GLOBAL.variable_name Oracle Naming Conventions.
System Variable is a SQL*Forms variable to keep track of some internal SQL*Forms state. Able to reference the value of system variable in order to control the way an application behaves. Value of system variable corresponds to the current form. They are Block_Status,Record_Status,Form_Status, Current_Block,Current_Field,Current_Form,Current_Value,Cursor_Block,Cursor_Field,Cursor_Record,Cursor_Value,Last_Record,Last_Query,Message_Level,Record_Status,Trigger_Block,Trigger_Field & Trigger_Record.
Features of Oracle 7 :
Stored Procedures is commonly used procedures can be written once in PL/SQL and stored in the database for repeated use by applications. This ensures consistent behavior among applications and reduce development & testing time. Centralizing the application logic and can be accessed from any Oracle tools.
Difference between Stored Procedure and Oracle Forms Procedure :
Stored Procedure Oracle Forms Procedure
Stored within the database. Stored within the Oracle Forms Appln.
Documented within the data dictionary. Documented from the Oracle Forms Appln.
Executed from any db tool or appln. Executed from an Oracle Forms appln. only.
May reference db stored procedures only. May reference Oracle Forms procedures in addition to db stored procedures.
Made available to applns. by means of db security. Made available to Oracle forms appln. by means of form-level security and the Copy/Reference facility.
Invoked independently of, and in addition to, Oracle Forms procedures. Invoked independently of, and in addition to, stored procedures.
Stored Package is a group of related Stored Procedures, Functions & other package constructs stored together as a unit in the db. Stored Package provides the db administrator or appln. developer organizational benefits, they also offer increased functionality and db perfomance.
QEP for Stored Procedures is generated at compile time.
Benefit from Stored Procedures & Functions : In addition to modularizing appln. development, other benefits are
Improve Data Security and Integrity :
Control indirect access to db objects from non-privileged users with security privileges.
Ensure that related actions are performed together, or not at all, by funneling activity for related tables thro¡¦ a single path.
Improve Performance :
Avoid reparsing for multiple users by exploiting shared SQL.
Avoid PL/SQL parsing at runtime by parsing at compile time.
Reduce the number of calls to the database and decrease network traffic by bundling commands.
Conserve Memory :
Store a single copy of code in the db to avoid multiple copies of the same code for diff. applns.
Share sql to avoid multiple cursors for different applns.
Improve Maintenance :
Modify routines online without interfering with other users.
Modify one routine to affect multiple applications.
Modify one routine to eliminate duplicate testing.
Database Triggers is a stored procedure that is implicitly fired when an Insert, Update or Delete statement is issued against the associated table. Complex business rules that cannot be enforced using declarative integrity constraints can be enforced using triggers. It is similar to procedures that are stored in the databases and implicitly fired when a table is modified.
Guidelines :
Use triggers to guarantee that when a specific operation is performed, related actions are performed.
Use DB triggers for centralized global operations that should be fired for triggering statement regardless of which user or database application issued the statement.
Do not define triggers to duplicate the functionality & do not create Recursive triggers.
Triggers will be compiled when it is fired. So, limit the size of triggers. Compilation of triggers smaller in size will have insignificant effect on system performance. If the trigger has to be execute many lines of code, include the code in the Stored Procedure.
Mutating Error in DB triggers is when a select statement within the scope of the trigger selects rows corresponding to the trigger table itself. It can be solved by placing the select statement in a stored procedure and calling the stored procedure from the scope of the trigger.
Differences between Oracle 6.0 & 7.0 :
Only not null was implemented in 6 where as in 7 all the integrity constraints are implemented i.e. Not Null, Primary, Foreign, Check, Default & Unique constraints.
Database Triggers, Stored Procedures, Functions & Packages are available in 7.
Roles : ORACLE provides for easy & controlled privilege management thro¡¦ the use of Roles. Roles are named groups of related privileges that are granted to users or other roles. The properties are Reduced granting of privileges, Dynamic privilege management, Selective availability of privileges & Application awareness.
Schemas is a collection of objects i.e. tables, views etc. and schema exists for each oracle user.
Profiles is assigned to each user that specifies limitations on several system resources available to the user i.e. the number of concurrent sessions the user can establish, the CPU processing time, the amount of logical I/O, the allowed amount of idle time for the user¡¦s session & the allowed amount of connect time for the user¡¦s session.
Cost Based Optimizer is available. It uses statistics about tables, along with info about the available indexes to select an execution plan for SQL statements. This allows even inexperienced users to submit complex queries without having to worry about the performance. If we know the better execution path, provide hints to it to allow it to select the proper execution path.
Table Replication is a snapshot of a table.
Multi threaded architecture several user process for a single server process and the user process can be configured.
Declarative Referential Integrity establishes precise rules for use of columns that are common across tables. Built into db software and enforced by default.
SQL*REPORTWriter :
Features :
Application development tool for designing & executing reports. ANSI standard SQL used to retrieve records in the report. Menu-driven, simple spreadsheet-style screens. Default values for report format. Ability to customize report format, date & number formats. Complex data relationships. Calculations & summaries. Text processing and highlighting features. Reports can be viewed immediately on-line for corrections. Generate reports interactively or in a production environment. Parameters provide run-time flexibility. Report management facility for easy report maintenance & Integration with Oracle application tools.
Components :
Query - retrieves data from the database. Group - used to cluster columns returned from the query. Fields - containers for data values. Summary - calculated summary function on a field. Text - physical areas of report. Report - dimensions, security and history of the report. Parameters - entered at run-time to control production, data values.
Queries : Every report must contain atleast one query. Query retrieves data for the report from database tables or views. Queries can be unrelated i.e Master/Master report. Related queries form a hierarchy, in which child query is executed once for each record returned by the parent. Can create relationships between queries. No limit to the number of queries in a report. No limit to the level of relationships (nesting) in queries. i.e. Master/Detail (parent/child) queries. Matrix queries i.e. Two parents/One child queries.
On-line report can be viewed either in Browse i.e. Page by page or Window i.e. scrolls horizontally and vertically through a page.
Groups : A group is a set of one or more columns. Every report must contain at least one group. Each query automatically generates one group consisting of all columns in the query.
Break Groups : A break is a set of groups generated from one query. Can create new groups (break groups) that group records by the distinct values of a column or set of columns. Group settings provide format control.
Field : A field is a container for values derived from columns or calculated column values in the SELECT statement. Computed fields created by user. System variables (page number, number of pages, date etc.). User exits & DML statements.
Summaries : Summaries calculate subtotals, grand totals, running totals & other standard functions on field values. All summaries are manually created. Multiple summaries may be computed on any field, including fields derived from user exits & system variables. Summary settings provide format control. Summaries may be referenced in queries.
Text Objects : Text objects represent the physical layout of the report. Text objects are used to manipulate positions of fields & summaries. Customize text. Add page numbering. Changes made on field, group & summary setting screens are reflected on all associated text objects that have not been edited. Text object changes are not dynamically reflected in field, group & summary settings.
Parameters : Parameters contain default values that can be modified for each report or with each interactive run. Parameters may be placed in queries, user exits & text. The default parameter value, width & data type applying to a report may be changed on the parameter screen. Parameters may be selected for appearance or may be changed at run-time on the run-time parameter form. Parameters may be entered from the command line with the sqlrep or runrep command.
System Parameters provide production control. They are DESTYPE-Device type i.e. Screen, File, Printer, Sysout & Mail. DESNAME-Destination of report i.e. File name, Printer name & Oracle*Mail user id or user list. DESFORMAT-Printer format (used when sending the report to a file, printer, stream, or Oracle*Mail). COPIES-Number of copies to print (used when sending the report to the printer). CURRENCY-Symbols to use for the dollar sign. THOUSANDS-Symbol to use for the comma. DECIMAL-Symbol to use for the period.
Query Parameters can be created to specify data for the report at run-time.
Bind Parameter binds in a specific value when the query is run. To create a bind parameter Include the parameter in the SELECT statement; precede the name with a colon. Specify a default value on the parameter screen, or enter the value at run-time.
Lexical Parameter : Insert a SQL clause when the query is run. May be used to replace WHERE, GROUP BY, ORDER BY, HAVING, CONNECT WITH, START WITH clauses. To create a lexical parameter Create a new record on the parameter screen. Enter the parameter name, data type & width. Enter the default value (SQL clause) on the Parameter screen. Include the parameter in the SELECT statement; precede the parameter name with &. Use the default value, or specify the value at run-time.
SQL*ReportWriter Utilities : SQLREP - Program used to design reports. GENREP - Generates a runfile for a report that has not been executed via the Action menu. RUNREP - Runs the reports (stored as runfiles) & creates final output. May be loaded on systems without SQLREP to produce reports. DUMPREP - Creates an ASCII file containing report definitions. LOADREP - Loads report definitions into an ORACLE database. PRINTDEF - Creates printer definitions. TERMDEF - Created terminal definitions. MOVEREP - SQL*ReportWriter V1.0 to V1.1 conversion program.
Matrix Reports : A matrix report has the following characteristics :
Matrix report is a grid containing three sets of data. Matrix Report require exactly three queries: two parents & one child. Each query has only one group. Each group must be identified as a matrix group. Print direction is Down for one group, Across for one group, and Cross tab for the third (the group of the child query). Summaries are placed by default in the group subfoots of the print group.
PRO*C :
Oracle Precompiler is a programming tool that allows to embed SQL statements in a high level source program. Precompiler accepts the source program as input, translates the embedded SQL statements into standard Oracle runtime library calls & generates a modified source program that can be compiled, linked & executed in the normal way.
Why use Precompiler : It allows to pack the power & flexibility of SQL into application programs. A convenient, easy to use interface lets your application access Oracle directly. Help to fine tune the application & saves time because the precompiler & not the user translates each embedded SQL statement into several native language Oracle calls.
Oracle Precompilers are full featured tools that support professional approach to embedded SQL programming. FIPS flagger helps to develop portable applications & to identify nonconforming SQL elements.
Embedded SQL Statements are divided into
Executable Declarative
Call to runtime library SQLLIB To declare Oracle objects, communication areas & SQL variables.
Connect to Oracle, to define query & manipulate data, to control access to data & to process transactions. Placed wherever host language host language executable statements can be placed. Placed wherever host language declarations can be placed.
For SQL statements, begin with keywords EXEC SQL & end with SQL statement terminator. For PL/SQL block, begin with EXEC SQL EXECUTE & END EXEC.
Host Variables are key to communication between Oracle and the program. Host variable is a scalar or array variable declared in the host language & shared with Oracle. Program uses i/p host variable to pass data to Oracle. Oracle uses o/p host variable to pass data & status info to the program. In SQL statements, the variable are prefixed with a colon.
Indicator Variables is an integer variable that indicates the value or condition of its host variable. Use indicator variable to assign nulls to i/p host variable & to detect nulls or truncated values in o/p host variables.
Oracle Precompiler offers two error handling mechanisms :
SQLCA is a data structure copied into your host program. It defines program variables used by Oracle to pass run time status info to the program. E.g. Check to see if a Delete was successful & how many rows were deleted. SQLCA is used to provide diagnostic checking & event handling.
ORACA is a data structure copied into your host program to handle ORACLE specific communications. When we need more run time info than SQLCA provides, we use ORACA. ORACA helps to monitor PRO*C programs use of ORACLE resources such as SQL statement executor & the cursor cache, an area of memory reserved for memory management.
SQLDA is a structure copied into your host program to process dynamic SQL statements that contains unknown number of select-list items or place holders for bind variables.
Whenever, we can specify actions to be taken automatically when oracle detects an error or warning condition. Actions include continuing with the next statement, calling a subroutine, branching to a labeled statement.
Precompiling adds a step to the traditional development process, but it lets to write very flexible applications.
PL/SQL blocks can be embedded in PRO*C. Stored Procedures can be called from PRO*C. Pointers can be used in PRO*C but it can't be used in SQL statements.
VARCHAR implementation in C after Precompilation : For most applications, use C pseudo type VARCHAR instead of standard C character arrays because Oracle does not null terminate strings. After precompilation, expands the Varchar declaration into a structure with array & length number.
Data Type Equivalencing is conversion from Oracle to C data type.
SQL*DBA :
Auditing : To aid in the investigation of suspicious db use. Statement Auditing is the auditing of specific SQL statements. Privilege Auditing is the auditing of the use of powerful system privileges. Object Auditing is the auditing of access to specific schema objects.
Audit Trial : Results of audited operations are stored in a table in data dictionary.
Physical DB Structure : ORACLE db consists of atleast one or more data files, two or more redo log files & one or more control files. The files of a db provide the actual physical storage for db info.
Logical DB Structure : ORACLE db consists of one or more tablespaces, the db schema¡¦s objects (i.e. tables, views, indexes, clusters, sequences, sp). Tablespaces, Segments, Extents dictate how physical space of a db is used.
Tablespaces : A db is divided into logical storage units called TS. TS is used to group related logical structures together. Each db is logically divided into one or more TS. One or more data files are explicitly created for each TS to physically store the data of all logical structures in a TS. Combined size of the data file is the total storage capacity of TS. Combined storage capacity of the TS¡¦s is the total storage capacity of the db.
Online & Offline TS : A TS can be online (accessible) or offline (not accessible). A TS can be offline to make portion of the db unavailable while allowing normal access for the remainder of the db to make administrative tasks easier.
Schema is a collection of objects. Schema Objects are the logical structures that directly refer to the db¡¦s data. Schema objects includes tables, views, sequences, synonyms, stored procedures, indexes, clusters & db links. No relation between ts & schema. Objects in same schema can be in diff. ts & vice versa.
Index Clusters are group of one or more tables physically stored together because they share common columns & are often used together. The related columns of the tables in a cluster is called cluster key. The data in a cluster key of an index cluster is store only once for multiple tables, so disk access time improves.
Hash Clusters : Also cluster table data in a manner similar to normal cluster. A row is stored in a hash cluster based on the result of applying a hash function to the row¡¦s cluster key value. All rows with the same hash key value are stored together on disk. Hash clusters are better than using indexed table or indexed clusters when a table is queried with equality queries. For such queries, the specified cluster key is hashed. The resulting hash key value points directly to the area on disk that stores the specified rows.
Database Links is a name object that describes a path from one db to another. DB links are implicitly used when a reference is made to a global object name in a distributed db.
Data Blocks : At the finest level of granularity, an ORACLE db¡¦s data is stored in data blocks. One data block corresponds to a specific number of bytes of physical db space on a disk. A data block size is specified when the db is created. A db uses & allocates free db space in ORACLE data blocks.
Extents is the next level of logical db space. An extent is a specific number of contiguous data blocks, obtained in a single allocation, used to store a specific type of info.
Segments is the next level of logical db storage above extent. A segment is a set of extents allocated for a certain logical structure. Different types are
Data Segment : Each non clustered table has a data segment. All the table¡¦s data is stored in the extents of its data segment. Each cluster has a data segment.
Index Segment : Each index has a index segment that stores all of its data.
Rollback Segment : One or more rollback segments are created by the db administrator for a db to temporarily store undo info.
Temporary Segments are created by ORACLE when a SQL statement needs a temporary work area to complete execution. When the statement finishes execution, the temp. segments extents are returned to the system for future use. ORACLE allocates space for all types of segments in extents. Therefore, when the existing extents of a segment are full, ORACLE allocates another extent for that segment as needed. Because extents are allocated as needed, the extents of a segment may or may not be contiguous on disk.
Data Files : ORACLE db should have atleast one or more physical data files. It contains all db data. A data file can be associated with only one db. Once created, a data file cannot change in size. One or more data files form a logical unit of db storage called a tablespace.
Redo Log Files : ORACLE db should have atleast two or more redo log files. The set of redo log files for a db is collectively known as the db¡¦s redo log. The primary function is to record all changes made to data. Should a failure prevent modified data from being permanently written to the data files, the changes can be obtained from redo log & work is never lost. Redo Log files are critical in protecting a db against failures. To protect against a failure involving the redo log itself, ORACLE allows a mirrored redo log so that two or more copies of the redo log can be maintained in diff. disks.
The use of Redo Log Files : The info in redo log file is used only to recovered the db from a system or media failure that prevents db data from being written to a db¡¦s data files.
Rolling Forward is the process of applying the redo log during a recovery operation.
Control Files : ORACLE db should have atleast one control file. A control file records the physical structure of the db. It contains db name, names & locations of db¡¦s data & redo log files & time stamp of db creation. Control files can be mirrored for protection of control files.
The use of Control Files : Every time an instance of an ORACLE db is started, its control file is used to identify the db & the redo log files that must be opened for db operation to proceed. DB¡¦s control file is also used if db recovery is necessary.
Data Dictionary : ORACLE db should have a data dictionary. The data dictionary of a ORACLE DB is a set of tables & views that are used as a read only reference about the db. It stores info about physical & logical structure of db. It also stored the info about valid users of an ORACLE db, info about integrity constraints defined for tables in the db & how much space is allocated for a schema object and how much of it is being used. DD is created when a db is created. The dd is critical to the operation of the db, which relies on the dd to record, verify and conduct ongoing work.
ORACLE has three basic memory structures to function - System Global Area (SGA), Program or Process Global Area (PGA) & Context Areas.
SGA is a shared memory region allocated by ORACLE that contain data & control info for one Oracle db instance. It is written to only by RDBMS processes. SGA & Oracle Background processes make up an Instance. SGA is allocated when an instance starts and deallocated when the instance is shut down. Data in SGA is shared among all users currently connected to the database. For optimal performance, the entire SGA should be as large as possible, to store as much data in memory as possible & minimize disk I/O. Most Oracle servers support only one Instance per Server. SGA contains Database Buffers, Redo Log Buffers & Shared Pool. These areas have fixed sizes are created at the instance startup.
DB Buffers Cache of the SGA store the most recently used blocks of db data; the set of db buffers in an instance is the db buffer cache. These buffers can contain modified data that has not been permanently written to the disk. Because the most recently used is kept in memory, less disk I/O is necessary and performance is increased. It consists of two blocks Data Segment Block & Rollback Segment Block.
During the course of transaction, changes to data are not written to the database file but these steps take place (a) Each statement executed in the transaction modifies the appropriate data segment block in the DB pool buffer. (b) Info that can be used to undo the transaction is stored in a Rollback block in the db buffer pool. (c) A record of each change made to Data & Rollback block is entered in a Redo Log Buffer. When transaction is committed, info in the redo log buffer is written to Redo Log File which are used in Recovery operations.
Redo Log Buffer of the SGA stores redo entries - a lot of changes made to the db. The redo entries stored in the redo log buffers are written to an online redo log file, which is used if db recovery is necessary. It size is static.
Shared Pool is a portion of the SGA that contains shared memory constructs such as Shared SQL areas. A shared SQL area is required to process every unique SQL statement submitted to a db. It contains info such as the parse tree and execution plan for the corresponding statement. A single shared SQL areas is used by multiple applns. that issue the same statement, leaving more shared memory for other uses.
PGA is a memory buffer that contains data & control info for a single client process. PGA is allocated on the server for each client that connects to the server. It contains info about connection & maintains info so that user can communicate with oracle. PGA includes Context Areas. PGA is a writeable, non-shared memory area. It is exclusive to the user processes & is read & written only by Oracle processes acting on behalf of the user.
Context Areas is a memory buffer of the Server that contains the current status of one SQL statement.
Virtual Memory is an OS feature that offers more apparent memory than is provided by real memory. Simulates memory by swapping RAM & Secondary storage.
Processes is a mechanism in an OS that can execute a series of steps. Some OS uses the terms job or tasks. A process normally has its own memory area in which it runs. It has two general type of processes
User (Client) Processes is created and maintained to execute the software code of an appln. program (Pro*C) or an ORACLE tool (SQL*DBA). It also manages the communication with the server process thro¡¦ program interface.
ORACLE Processes are called by other processes to perform functions on behalf of the invoking process. Diff. types of Oracle processes are
Server Processes : ORACLE creates server processes to handle requests from connected user processes. A server process is in charge of communicating with the user process and interacting with ORACLE to carry out requests of the associated user process. Can be configured to vary the number of user processes per server process
In a dedicated server config, a server process handles requests for a single user process. A multi threaded config. allows many user process to share a small number of server processes, minimizing the number of server processes and maximizing the utilization of available system resources & the user and server processes should be separate.
Background Process : ORACLE creates a set of background processes for each instance. They consolidate functions that would otherwise handled by multiple ORACLE programs running for each user process. They asynchronously perform I/O & monitor other ORACLE processes to provide increased parallelism for better performance & reliability. BG processes are given below.
Database Writer (DBWR) processes writes modified blocks from the database buffer cache to the database files. Blocks are written in proper order to maintain database integrity. DBWR is optimized to minimize disk writes. DBWR writes only when more data needs to be read into the SGA and too few db buffers free. The least recently used data is written to the data files first.
Log Writer (LGWR) processes writes redo log entries to disk when transaction is committed & the log buffer fills. Redo Log data is generated in the redo log buffer of the SGA.
Checkpoint (CKPT) : At specific times, all modified db buffers in the SGA are written to the data files by DBWR; this event is called a checkpoint. The checkpoint process is responsible for signaling DBWR at checkpoints and updating all data & control files of the db to indicate the most recent checkpoint. CKPT is optional; LGWR assumes the responsibilities of CKPT, if CKPT is not present.
System Monitor (SMON) performs instance recover at instance startup. In a multiple instance system i.e. Parallel Server, SMON of one instance can also perform instance recovery for other instances that have failed. SMON also cleans up temporary segments that are no longer in use & recovers dead transactions skipped during crash & instance recovery because of file read or offline errors. These transactions are eventually recovered by SMON when the tb or file is brought back online. SMON also coalesces free extents within the db, to make free space contiguous and easier to allocate.
Process Monitor (PMON) processes perform recovery when a user process fails. PMON is responsible for cleaning up the cache and freeing resources that the process was using. PMON also checks on dispatcher and server processes and restarts them if they have failed.
Archive (ARCH) processes copies on-line redo log files to on-line archival storage when they are full.
ARCH is active only when a db¡¦s redo log is used in ARCHIVELOG mode.
Recoverer (RECO) : The recoverer is used to resolve distributed transactions that are pending due to a network or system failure in a distributed db. At timed intervals, the local RECO attempts to connect to remote dbs and automatically complete the commit or rollback of the local portion of any pending distributed transactions.
Dispatcher (Dnnn) : Dispactchers are optional background processes, present only when a multi-threaded server configuration is used. At least one dispatcher process is created for every communication protocol in use. Each dispatcher process is responsible for routing requests from connected user processes to available shared server processes and returning the responses back to the appropriate user processes.
Lock (LCKn) : Up to ten lock processes are used for inter-instance locking when the ORACLE parallel server is used.
Network Listener (NLSN) process listens to network for connection requests made to server by client applications. When it detects, it starts a Shadow process that performs all further server communication with a client.
Oracle Instance : Every time a database is started on a server, an SGA is allocated & five background processes are started. The combination of these processes & memory buffers is an Instance.
SQL*Net is ORACLE¡¦s interface to standard communications protocols that allows for the proper transmission of data between computers.
ORACLE Parallel Server : Multiple Instance Systems : Some hardware architectures i.e. loosely coupled processors allow multiple computers to share access of data, software or peripheral devices. ORACLE with the Parallel Server option can take advantage of such architecture by running multiple instances that share a single physical db. In appropriate applications, ORACLE Parallel Server allows access to a single db by the users on multiple machines with increased performance.
Example of how ORACLE works : The following illustrates an configuration where the user and the associated server process are on separate machines.
1. An instance is currently running on a computer that is executing ORACLE i.e. DB Server.
2. A computer used to run an appln. i.e. client ws runs the appln. in a user process. The client attempts to establish a connection to the server using the proper SQL*Net. driver.
3. The server is running proper SQL*Net driver & the server detects the connection request from the appln. and creates a (dedicated) server process on behalf of the user process.
4. The user creates a SQL statement and commits the transaction. E.g. changes a name in a row of a table.
5. The server process receives the statement and checks the shared pool for any shared SQL area that contains an identical SQL statement. If a shared SQL area is found, the server process checks the user¡¦s access privileges to the requested data and the previously existing shared SQL is used to process the statement; if not, a new shared SQL area is allocated for the statement so that it can be parsed and processed.
6. The server process retrieves any necessary data values from the actual data file or those stored in SGA.
7. The server process modifies data in the SGA. The DBWR process writes modified blocks permanently to disk when doing so is efficient. Because the transaction committed, the LGWR process immediately records the transaction in the online redo log file.
8. If the transaction is successful, the server process send a message across the network to the appln. If it is not successful, an appropriate error message is transmitted.
9. Throughout this entire procedure, the other background processes run, watching for conditions that require intervention. In addition, the db server manages other users transactions and prevents contention between transaction that request the same data.
Trusted ORACLE : is ORACLE corp. multilevel secure DBMS product. It is designed to provide high level of secure data management capabilities required by organizations processing sensitive or classified info. It enforces Mandatory Access Control (MAC) which is mean of restricting access to info based on labels.
Distributed Processing uses more than one processor to divide the processing for a set of related jobs. Reduces the processing load on a single processor by allowing different processors to concentrate on a subset of related tasks, thus improving the performance. An ORACLE db system can easily take advantage of the distributed processing by using its client server architecture.
Distributed Databases is a network of db¡¦s managed by multiple db servers that appears to a user as a single logical db. The data of all db¡¦s in the distributed db can be simultaneously accessed and modified. Benefit is data of physically separate db¡¦s can be logically combined & potentially made accessible to all users on a nw. The db to which a user is directly connected is known as local db. Any additional db¡¦s accessed are called remote db. Distributed db allows increased access to a large amount of data across a nw, it must also provide the ability to hide the location of the data (Location Transparency) & hide the complexity of accessing it across the nw. Site Autonomy i.e. each db participating in a distributed db is administered separately & independently from the other db¡¦s, as though each db was a non-networked db.
Distributed Data Manipulation : To query a table named emp in the remote db SALES select * from emp@sales.
Two Phase Commit mechanism guarantees that all db servers participating in a distributed transaction either all commit or all roll back the statements in the transaction. Consists of two phases
Prepare Phase : The global coordinator (initiating node) asks participants to prepare (to promise to commit or rollback the transaction, even if there is a failure).
Commit Phase : If all participants respond to the coordinator that they are prepared, the coordinator asks all nodes to commit the transaction; if all participants cannot prepare, the coordinator asks all nodes to roll back the transaction.
Table Replication : Distributed db systems often locally replicate remote tables that are frequently queried by local users. By having read-only copies of heavily accessed data on several nodes, the distd. db does not need to send info across a nw repeatedly, thus helping to maximize the performance of the db appln. ORACLE provides automatic method for table replication & update called Snapshots.
Snapshots are read-only copies of a master table located on a remote node. Can be queried but not updated.
Optimization is to choose the most efficient way to execute a SQL statement.
Execution Plan : To execute a DML statement, ORACLE may have to physically retrieves rows of data from the db or prepares them in some way for the user issuing the statement.. The combination of the steps the optimizer chooses to execute a statement is called an execution plan.
Explain Plan : Examine the execution plan chosen by the optimizer for a SQL statement by using this command. This command causes the optimizer to choose the execution plan and then inserts data describing the plan into a db table.
Rule based approach : The optimizer chooses an execution plan based on the access paths available and the ranks of these access paths in table. If there is more than one way to execute an SQL statement, this approach uses the operation with the lower rank. Operation of lower rank executes faster than those associated with constructs with higher rank.
Cost based approach : The optimizer generates a set of potential execution plan for the statement based on its available access paths and hints.
The optimizer estimates the cost of each execution plan based on data distribution and storage characteristics statistics for the tables, clusters and indexes in the data dictionary. The cost is an estimated value proportional to the expected elapsed time needed to execute the statement using the execution plan. The optimizer calculates the cost based on the estimated computer resources including but not limited to I/O, CPU time and memory required to execute the statement using the plan. Execution plans with greater costs take more time to execute than those with smaller costs.
The optimizer compares the cost of the execution plans and chooses one with the smaller cost.
Goal of the Cost based Approach is the best throughput or minimal elapsed time necessary to process all rows accessed by the statement.
Statistics used for the Cost based approach : This approach uses statistics to estimate the cost of each execution plan. These statistics quantify the data distribution and storage characteristics of tables, columns and indexes. These statistics are generated using the ANALYZE command. Using these statistics, the optimizer estimates how much I/O, CPU time, and memory are required to execute a SQL statement using a particular execution plan.
The statistics are visible through these tables in the data dictionary.
USER_TABLES, ALL_TABLES & DBA_TABLES.
USER_TAB_COLUMNS, ALL_TAB_COLUMNS & DBA_TAB_COLUMNS.
USER_INDEXES, ALL_ INDEXES & DBA_ INDEXES.
USER_CLUSTERS & DBA_CLUSTERS.
ORACLE Optimizes SQL statements : For any SQL statement processes by ORACLE, the optimizer performs these tasks.
Evaluation of expressions and conditions : The optimizer first evaluates expressions and conditions containing constants as fully as possible.
Statement Transformation : For a complex statement, the optimizer may transform the original statement into an equivalent join statement.
View Merging : For a SQL statement that access a view, the optimizer often merges the views query into the original statement or the original statement into the view¡¦s query and then optimizes the result.
Choice of Optimization approaches : Chooses either a rule based or cost based based to optimization.
Choice of Access Paths : For each table accessed by the statement, the optimizer chooses one or more of the available access paths to obtain the table¡¦s data.
Choice of Join Orders : For a join statement that joins more than two tables, the optimizer chooses which pair of tables is joined first, and then which table is joined to the result.
Choice of Join Operations : For any join statement, the optimizer chooses an operation to use to perform the join.
Important Questions in Oracle, Developer /2000(Form 4.5 and Reports 2.5)
Oracle :
1) What are the Back ground processes in Oracle and what are they.
This is one of the most frequently asked question.There are basically 9 Processes but in a general system we need to mention the first five background processes.They do the house keeping activities for the Oracle and are common in any system.
The various background processes in oracle are
a) Data Base Writer(DBWR) : Data Base Writer Writes Modified blocks from Database buffer cache to Data Files.This is required since the data is not written whenever a transaction is commited.
b) LogWriter(LGWR) : LogWriter writes the redo log entries to disk. Redo Log data is generated in redo log buffer of SGA. As transaction commits and log buffer fills, LGWR writes log entries into a online redo log file.
c) System Monitor(SMON) : The System Monitor performs instance recovery at instance startup.This is useful for recovery from system failure
d) Process Monitor(PMON) : The Process Monitor peforms process recovery when user Process fails. Pmon Clears and Frees resources that process was using.
e) CheckPoint(CKPT) : At Specified times, all modified database buffers in SGA are written to data files by DBWR at Checkpoints and Updating all data files and control files of database to indicate the most recent checkpoint
f) Archieves(ARCH) : The Archiver copies online redo log files to archival storal when they are busy.
g) Recoveror(RECO) : The Recoveror is used to resolve the distributed transaction in network
h) Dispatcher (Dnnn) : The Dispatcher is useful in Multi Threaded Architecture
i) Lckn : We can have upto 10 lock processes for inter instance locking in parallel sql.
2) How many types of Sql Statements are there in Oracle
There are basically 6 types of sql statments.They are
a) Data Defination Language(DDL) : The DDL statments define and maintain objects and drop objects.
b) Data Manipulation Language(DML) : The DML statments manipulate database data.
c) Transaction Control Statements : Manage change by DML
d) Session Control : Used to control the properties of current session enabling and disabling roles and changing .e.g Alter Statements,Set Role
e) System Control Statements : Change Properties of Oracle Instance .e.g:: Alter System
f) Embedded Sql : Incorporate DDL,DML and T.C.S in Programming Language.e.g:: Using the Sql Statements in languages such as 'C', Open,Fetch, execute and close
3) What is a Transaction in Oracle
A transaction is a Logical unit of work that compromises one or more SQL Statements executed by a single User. According to ANSI, a transaction begins with first executable statment and ends when it is explicitly commited or rolled back.
4) Key Words Used in Oracle
The Key words that are used in Oracle are
a) Commiting : A transaction is said to be commited when the transaction makes
permanent changes resulting from the SQL statements.
b) Rollback : A transaction that retracts any of the changes resulting from SQL
statements in Transaction.
c) SavePoint : For long transactions that contain many SQL statements, intermediate
markers or savepoints are declared. Savepoints can be used to divide a transactino into smaller points.
d) Rolling Forward : Process of applying redo log during recovery is called rolling
forward.
e) Cursor : A cursor is a handle ( name or a pointer) for the memory associated with a
specific stament. A cursor is basically an area allocated by Oracle for executing the Sql Statement. Oracle uses an implicit cursor statement for Single row query and Uses Explcit cursor for a multi row query.
f) System Global Area(SGA) : The SGA is a shared memory region allocated by the
Oracle that contains Data and control information for one Oracle Instance.It consists of Database Buffer Cache and Redo log Buffer.
g) Program Global Area (PGA) : The PGA is a memory buffer that contains data and
control information for server process.
h) Database Buffer Cache : Databese Buffer of SGA stores the most recently used
blocks of datatbase data.The set of database buffers in an instance is called Database Buffer Cache.
i) Redo log Buffer : Redo log Buffer of SGA stores all the redo log entries.
j) Redo Log Files : Redo log files are set of files that protect altered database data in
memory that has not been written to Data Files. They are basically used for backup when a database crashes.
k) Process : A Process is a 'thread of control' or mechansim in Operating System that
executes series of steps.
5) What are Procedure,functions and Packages
Procedures and functions consist of set of PL/SQL statements that are grouped together as a unit to solve a specific problem or perform set of related tasks.
Procedures do not Return values while Functions return one One Value
Packages Provide a method of encapsulating and storing related procedures, functions, variables and other Package Contents
6) What are Database Triggers and Stored Procedures
Database Triggers :: Database Triggers are Procedures that are automatically executed as a result of insert in, update to, or delete from table. Database triggers have the values old and new to denote the old value in the table before it is deleted and the new indicated the new value that will be used. DT are useful for implementing complex business rules which cannot be enforced using the integrity rules.We can have the trigger as Before trigger or After Trigger and at Statement or Row level.
eg. operations insert,update ,delete 3 before ,after 3*2 A total of 6 combinatons
At statment level(once for the trigger) or row level( for every execution ) 6 * 2 A total of 12. Thus a total of 12 combinations are there and the restriction of usage of 12 triggers has been lifted from Oracle 7.3 Onwards.
Stored Procedures : Stored Procedures are Procedures that are stored in Compiled form in the database.The advantage of using the stored procedures is that many users can use the same procedure in compiled and ready to use format.
7) How many Integrity Rules are there and what are they
There are Three Integrity Rules. They are as follows ::
a) Entity Integrity Rule : The Entity Integrity Rule enforces that the Primary key cannot be Null
b) Foreign Key Integrity Rule : The FKIR denotes that the relationship between the foreign key and the primary key has to be enforced.When there is data in Child Tables the Master tables cannot be deleted.
c) Business Integrity Rules : The Third Intigrity rule is about the complex business processes which cannot be implemented by the above 2 rules.
8) What are the Various Master and Detail Relation ships.
The various Master and Detail Relationship are
a) NonIsolated : The Master cannot be deleted when a child is exisiting
b) Isolated : The Master can be deleted when the child is exisiting
c) Cascading : The child gets deleted when the Master is deleted.
9) What are the Various Block Coordination Properties
The various Block Coordination Properties are
a) Immediate Default Setting. The Detail records are shown when the Master Record are shown.
b) Deffered with Auto Query Oracle Forms defer fetching the detail records until the operator navigates to the detail block.
c) Deffered with No Auto Query The operator must navigate to the detail block and explicitly execute a query
10) What are the Different Optimisation Techniques
The Various Optimisation techniques are
a) Execute Plan : we can see the plan of the query and change it accordingly based on the indexes
b)Optimizer_hint: set_item_property('DeptBlock',OPTIMIZER_HINT,'FIRST_ROWS');
Select /*+ First_Rows */ Deptno,Dname,Loc,Rowid from dept where (Deptno > 25)
c) Optimize_Sql : By setting the Optimize_Sql = No, Oracle Forms assigns a single cursor for all SQL statements.This slow downs the processing because for evertime the SQL must be parsed whenver they are executed.
f45run module = my_firstform userid = scott/tiger optimize_sql = No
d) Optimize_Tp : By setting the Optimize_Tp= No, Oracle Forms assigns seperate cursor only for each query SELECT statement. All other SQL statements reuse the cursor.
f45run module = my_firstform userid = scott/tiger optimize_Tp = No
11) How do u implement the If statement in the Select Statement
We can implement the if statement in the select statement by using the Decode statement.
e.g select DECODE (EMP_CAT,'1','First','2','Second'Null);
Here the Null is the else statement where null is done .
12) How many types of Exceptions are there
There are 2 types of exceptions. They are
a) System Exceptions
e.g. When no_data_found, When too_many_rows
b) User Defined Exceptions
e.g. My_exception exception
When My_exception then
13) What are the inline and the precompiler directives
The inline and precompiler directives detect the values directly
14) How do you use the same lov for 2 columns
We can use the same lov for 2 columns by passing the return values in global values and using the global values in the code
15) How many minimum groups are required for a matrix report
The minimum number of groups in matrix report are 4
16) What is the difference between static and dynamic lov
The static lov contains the predetermined values while the dynamic lov contains values that come at run time
17) What are snap shots and views
Snapshots are mirror or replicas of tables. Views are built using the columns from one or more tables. The Single Table View can be updated but the view with multi table cannot be updated
18) What are the OOPS concepts in Oracle.
Oracle does implement the OOPS concepts. The best example is the Property Classes. We can categorise the properties by setting the visual attributes and then attach the property classes for the objects. OOPS supports the concepts of objects and classes and we can consider the peroperty classes as classes and the items as objects
19) What is the difference between candidate key, unique key and primary key
Candidate keys are the columns in the table that could be the primary keys and the primary key is the key that has been selected to identify the rows. Unique key is also useful for identifying the distinct rows in the table.
20) What is concurrency
Cuncurrency is allowing simultaneous access of same data by different users. Locks useful for accesing the database are
a) Exclusive
The exclusive lock is useful for locking the row when an insert,update or delete is being done.This lock should not be applied when we do only select from the row.
b) Share lock
We can do the table as Share_Lock as many share_locks can be put on the same resource.
21) Previleges and Grants
Previleges are the right to execute a particulare type of SQL statements.
eg. Right to Connect, Right to create, Right to resource
Grants are given to the objects so that the object might be accessed accordingly.The grant has to be given by the owner of the object.
22) Table Space,Data Files,Parameter File, Control Files
Table Space : The table space is useful for storing the data in the database.When a database is created two table spaces are created.
a) System Table space : This data file stores all the tables related to the system and dba tables
b) User Table space : This data file stores all the user related tables
We should have seperate table spaces for storing the tables and indexes so that the access is fast.
Data Files : Every Oracle Data Base has one or more physical data files.They store the data for the database.Every datafile is associated with only one database.Once the Data file is created the size cannot change.To increase the size of the database to store more data we have to add data file.
Parameter Files : Parameter file is needed to start an instance.A parameter file contains the list of instance configuration parameters e.g.::
db_block_buffers = 500
db_name = ORA7
db_domain = u.s.acme lang
Control Files : Control files record the physical structure of the data files and redo log files. They contain the Db name, name and location of dbs, data files ,redo log files and time stamp.
23) Physical Storage of the Data
The finest level of granularity of the data base are the data blocks.
Data Block : One Data Block correspond to specific number of physical database space
Extent : Extent is the number of specific number of contigious data blocks.
Segments : Set of Extents allocated for Extents. There are three types of Segments
a) Data Segment : Non Clustered Table has data segment data of every table is stored in
cluster data segment
b) Index Segment : Each Index has index segment that stores data
c) Roll Back Segment : Temporarily store 'undo' information
24) What are the Pct Free and Pct Used
Pct Free is used to denote the percentage of the free space that is to be left when creating a table. Similarly Pct Used is used to denote the percentage of the used space that is to be used when creating a table
eg. Pctfree 20, Pctused 40
25) What is Row Chaining
The data of a row in a table may not be able to fit the same data block.Data for row is stored in a chain of data blocks .
26) What is a 2 Phase Commit
Two Phase commit is used in distributed data base systems. This is useful to maintain the integrity of the database so that all the users see the same values. It contains DML statements or Remote Procedural calls that reference a remote object. There are basically 2 phases in a 2 phase commit.
a) Prepare Phase : Global coordinator asks participants to prepare
b) Commit Phase : Commit all participants to coordinator to Prepared, Read only
or abort Reply
27) What is the difference between deleting and truncating of tables
Deleting a table will not remove the rows from the table but entry is there in the database dictionary and it can be retrieved But truncating a table deletes it completely and it cannot be retrieved.
28) What are mutating tables
When a table is in state of transition it is said to be mutating. eg :: If a row has been deleted then the table is said to be mutating and no operations can be done on the table except select.
29) What are Codd Rules
Codd Rules describe the ideal nature of a RDBMS. No RDBMS satisfies all the 12 codd rules and Oracle Satisfies 11 of the 12 rules and is the only Rdbms to satisfy the maximum number of rules.
30) What is Normalisation
Normalisation is the process of organising the tables to remove the redundancy.There are mainly 5 Normalisation rules.
a) 1 Normal Form : A table is said to be in 1st Normal Form when the attributes are
atomic
b) 2 Normal Form : A table is said to be in 2nd Normal Form when all the candidate
keys are dependant on the primary key
c) 3rd Normal Form : A table is said to be third Normal form when it is not dependant
transitively
31) What is the Difference between a post query and a pre query
A post query will fire for every row that is fetched but the pre query will fire only once.
32) Deleting the Duplicate rows in the table
We can delete the duplicate rows in the table by using the Rowid
33) Can U disable database trigger? How?
Yes. With respect to table
ALTER TABLE TABLE
[[ DISABLE all_trigger ]]
34) What is pseudo columns ? Name them?
A pseudocolumn behaves like a table column, but is not actually stored in the table. You can select from pseudocolumns, but you cannot insert, update, or delete their values. This section describes these pseudocolumns:
* CURRVAL
* NEXTVAL
* LEVEL
* ROWID
* ROWNUM
35) How many columns can table have?
The number of columns in a table can range from 1 to 254.
36) Is space acquired in blocks or extents ?
In extents .
37) what is clustered index?
In an indexed cluster, rows are stored together based on their cluster key values . Can not applied for HASH.
38) what are the datatypes supported By oracle (INTERNAL)?
Varchar2, Number,Char , MLSLABEL.
39 ) What are attributes of cursor?
%FOUND , %NOTFOUND , %ISOPEN,%ROWCOUNT
40) Can you use select in FROM clause of SQL select ?
Yes.
Forms 4.5 Questions
1) Which trigger are created when master -detail rela?
master delete property
* NON-ISOLATED (default)
a) on check delete master
b) on clear details
c) on populate details
* ISOLATED
a) on clear details
b) on populate details
* CASCADE
a) per-delete
b) on clear details
c) on populate details
2) which system variables can be set by users?
SYSTEM.MESSAGE_LEVEL
SYSTEM.DATE_THRESHOLD
SYSTEM.EFFECTIVE_DATE
SYSTEM.SUPPRESS_WORKING
3) What are object group?
An object group is a container for a group of objects. You define an object group when you want to package related objects so you can copy or reference them in another module.
4) What are referenced objects?
Referencing allows you to create objects that inherit their functionality and appearance from other objects. Referencing an object is similar to copying an object, except that the resulting reference object maintains a link to its source object. A reference object automatically inherits any changes that have been made to the source object when you open or regenerate the module that contains the reference object.
5) Can you store objects in library?
Referencing allows you to create objects that inherit their functionality and appearance from other objects. Referencing an object is similar to copying an object, except that the resulting reference object maintains a link to its source object. A reference object automatically inherits any changes that have been made to the source object when you open or regenerate the module that contains the reference object.
6) Is forms 4.5 object oriented tool ? why?
yes , partially. 1) PROPERTY CLASS - inheritance property
2) OVERLOADING : procedures and functions.
7) Can you issue DDL in forms?
yes, but you have to use FORMS_DDL.
Referencing allows you to create objects that inherit their functionality and appearance from other objects. Referencing an object is similar to copying an object, except that the resulting reference object maintains a link to its source object. A reference object automatically inherits any changes that have been made to the source object when you open or regenerate the module that contains the reference object.
Any string expression up to 32K:
¡P a literal
¡P an expression or a variable representing the text of a block of dynamically
created PL/SQL code
¡P a DML statement or
¡P a DDL statement
Restrictions:
The statement you pass to FORMS_DDL may not contain bind variable references in the string, but the values of bind variables can be concatenated into the string before passing the result to FORMS_DDL.
8) What is SECURE property?
Hides characters that the operator types into the text item. This setting is typically used for password protection.
9 ) What are the types of triggers and how the sequence of firing in text item
Triggers can be classified as Key Triggers, Mouse Triggers ,Navigational Triggers.
Key Triggers : Key Triggers are fired as a result of Key action.e.g : Key-next-field, Key-up,Key-Down Mouse Triggers : Mouse Triggers are fired as a result of the mouse navigation.e.g. When-mouse-button-presed,when-mouse-doubleclicked,etc
Navigational Triggers : These Triggers are fired as a result of Navigation. E.g : Post-Text-item,Pre-text-item. We also have event triggers like when -new-form-instance and when-new-block-instance.
We cannot call restricted procedures like go_to(¡¥my_block.first_item¡¦) in the Navigational triggers . But can use them in the Key-next-item. The Difference between Key-next and Post-Text is an very important question. The key-next is fired as a result of the key action while the post text is fired as a result of the mouse movement. Key next will not fire unless there is a key event.
The sequence of firing in a text item are as follows ::
a) pre - text
b) when new item
c) key-next
d) when validate
e) post text
10 ) Can you store pictures in database? How?
Yes , in long Raw datatype.
11) What are property classes ? Can property classes have trigger?
Property class inheritance is a powerful feature that allows you to quickly define objects that conform to your own interface and functionality standards. Property classes also allow you to make global changes to applications quickly. By simply changing the definition of a property class, you can change the definition of all objects that inherit properties from that class. Yes . All type of triggers .
12) If you have property class attached to an item and you have same trigger written for the
item . Which will fire first?
Item level trigger fires , If item level trigger fires, property level trigger won't fire. Triggers at the lowest level are always given the first preference. The item level trigger fires first and then the block and then the Form level trigger.
13) What are record groups ? Can record groups created at run-time?
A record group is an internal Oracle Forms data structure that has a column/row framework similar to a database table. However, unlike database tables, record groups are separate objects that belong to the form module in which they are defined. A record group can have an unlimited number of columns of type CHAR, LONG, NUMBER, or DATE provided that the total number of columns does not exceed 64K.Record group column names cannot exceed 30 characters. Programmatically, record groups can be used whenever the functionality offered by a two-dimensional array of multiple data types is desirable.
TYPES OF RECORD GROUP:
Query Record Group A query record group is a record group that has an associated SELECT statement.
The columns in a query record group derive their default names, data types, and lengths from the database columns referenced in the SELECT statement. The records in a query record group are the rows retrieved by the query associated with that record group.
Non-query Record Group A non-query record group is a group that does not have an associated query, but whose structure and values can be modified programmatically at runtime.
Static Record Group A static record group is not associated with a query; rather, you define its structure and row values at design time, and they remain fixed at runtime.
14) What are ALERT?
An ALERT is a modal window that displays a message notifiying operator of some application condition.
15) Can a button have icon and lable at the same time ?
-NO
16) What is mouse navigate property of button?
When Mouse Navigate is True (the default), Oracle Forms performs standard navigation to move the focus to the item when the operator activates the item with the mouse.
When Mouse Navigate is set to False, Oracle Forms does not perform navigation (and the resulting validation) to move to the item when an operator activates the item with the mouse.
17) What is FORMS_MDI_WINDOW?
Forms run inside the MDI application window. This property is useful for calling a form from another one.
18) What are timers ? when when-timer-expired does not fire?
The When-Timer-Expired trigger can not fire during trigger, navigation, or transaction processing.
19) Can object group have a block?
Yes , object group can have block as well as program units.
20) How many types of canvases are there.
There are 2 types of canvases called as Content and Stack Canvas. Content canvas is the default and the one that is used mostly for giving the base effect. Its like a plate on which we add items and stacked canvas is used for giving 3 dimensional effect.
These are some other questions that may be asked
1) What are user-exits?
It invokes 3GL programs.
2) Can you pass values to-and-fro from foreign function ? how ?
Yes . You obtain a return value from a foreign function by assigning the return value to an Oracle Forms variable or item. Make sure that the Oracle Forms variable or item is the same data type as the return value from the foreign function. After assigning an Oracle Forms variable or item value to a PL/SQL variable, pass the PL/SQL variable as a parameter value in the PL/SQL interface of the foreign function. The PL/SQL variable that is passed as a parameter must be a valid PL/SQL data type; it must also be the appropriate parameter type as defined in the PL/SQL interface.
3) What is IAPXTB structure ?
The entries of Pro * C and user exits and the form which simulate the proc or user_exit are stored in IAPXTB table in d/b.
4) Can you call WIN-SDK thruo' user exits?
YES.
5) Does user exits supports DLL on MSWINDOWS ?
YES .
6) What is path setting for DLL?
Make sure you include the name of the DLL in the FORMS45_USEREXIT variable of the ORACLE.INI file, or rename the DLL to F45XTB.DLL. If you rename the DLL to F45XTB.DLL, replace the existing F45XTB.DLL in the ORAWINBIN directory with the new F45XTB.DLL.
7) How is mapping of name of DLL and function done?
The dll can be created using the Visual C++ / Visual Basic Tools and then the dll is put in the path that is defined the registery.
8) what is precompiler?
It is similar to C precompiler directives.
9) Can you connect to non - oracle datasource ? How?
Yes .
10 ) what are key-mode and locking mode properties? level ?
Key Mode : Specifies how oracle forms uniquely identifies rows in the database.This is
property includes for application that will run against NON-ORACLE
datasources .
Key setting unique (default.)
dateable
n-updateable.
Locking mode : Specifies when Oracle Forms should attempt to obtain database locks on
rows that correspond to queried records in the form.
a) immediate b) delayed
11) What are savepoint mode and cursor mode properties ? level?
Specifies whether Oracle Forms should issue savepoints during a session. This property is included primarily for applications that will run against non-ORACLE data sources. For applications that will run against ORACLE, use the default setting.
Cursor mode - define cursur state across transaction
Open/close.
12) What is transactional trigger property?
Identifies a block as transactional control block. i.e. non - database block that oracle forms should manage as transactional block.(NON-ORACLE datasource) default - FALSE.
13) What is OLE automation ?
OLE automation allows an OLE server application to expose a set of commands and functions that can be invoked from an OLE container application. OLE automation provides a way for an OLE container application to use the features of an OLE server application to manipulate an OLE object from the OLE container environment. (FORMS_OLE)
14) What does invoke built-in do?
This procedure invokes a method.
Syntax:
PROCEDURE OLE2.INVOKE
(object obj_type,
method VARCHAR2,
list list_type := 0);
Parameters:
object Is an OLE2 Automation Object.
method Is a method (procedure) of the OLE2 object.
list Is the name of an argument list assigned to the
OLE2.CREATE_ARGLIST function.
15) What are OPEN_FORM,CALL_FORM,NEW_FORM? diff?
CALL_FORM : It calls the other form. but parent remains active, when called form
completes the operation , it releases lock and control goes back to the calling form. When you call a form, Oracle Forms issues a savepoint for the called form. If the
CLEAR_FORM function causes a rollback when the called form is current, Oracle Forms
rolls back uncommitted changes to this savepoint.
OPEN_FORM : When you call a form, Oracle Forms issues a savepoint for the called
form. If the
CLEAR_FORM function causes a rollback when the called form is current, Oracle Forms
rolls back uncommitted changes to this savepoint.
NEW_FORM : Exits the current form and enters the indicated form.The calling form is
terminated as the parent form. If the calling form had been called by a higher form, Oracle Forms keeps the higher call active and treats it as a call to the new form. Oracle Forms releases memory (such as database cursors) that the terminated form was using. Oracle Forms runs the new form with the same Runform options as the parent form. If the parent form was a called form, Oracle Forms runs the new form with the same options as the parent form.
16 ) What is call form stack?
When successive forms are loaded via the CALL_FORM procedure, the resulting module hierarchy is known as the call form stack.
17) Can u port applictions across the platforms? how?
Yes we can port applications across platforms.Consider the form developed in a windows system.The form would be generated in unix system by using f45gen my_form.fmb scott/tiger
GUI
1) What is a visual attribute?
Visual attributes are the font, color, and pattern properties that you set for form and menu objects that appear in your application's interface.
2) Diff. between VAT and Property Class? imp
Named visual attributes define only font, color, and pattern attributes; property classes can contain these and any other properties.You can change the appearance of objects at runtime by changing the named visual attribute programmatically; property class assignment cannot be changed programmatically. When an object is inheriting from both a property class and a named visual attribute, the named visual attribute settings take precedence, and any visual attribute properties in the class are ignored.
3 ) Which trigger related to mouse?
* When-Mouse-Click
* When-Mouse-DoubleClick
* When-Mouse-Down
* When-Mouse-Enter
* When-Mouse-Leave
* When-Mouse-Move
* When-Mouse-Up
4) What is Current record attribute property?
Specifies the named visual attribute used when an item is part of the current record.
Current Record Attribute is frequently used at the block level to display the current row in a multi-record If you define an item-level Current Record Attribute, you can display a pre-determined item in a special color when it is part of the current record, but you cannot dynamically highlight the current item, as the input focus changes.
5) Can u change VAT at run time?
Yes. You can programmatically change an object's named visual attribute setting to change the font, color, and pattern of the object at runtime.
6) Can u set default font in forms?
Yes. Change windows registry(regedit). Set form45_font to the desired font.
7) Can u have OLE objects in forms?
Yes.
8) Can u have VBX and OCX controls in forms ?
Yes.
9) What r the types of windows (Window style)?
Specifies whether the window is a Document window or a Dialog window.
10) What is OLE Activation style property?
Specifies the event that will activate the OLE containing item.
11) Can u change the mouse pointer ? How?
Yes. Specifies the mouse cursor style. Use this property to dynamically change the shape of the cursor.
Reports 2.5
1) How many types of columns are there and what are they
Formula columns : For doing mathematical calculations and returning one value
Summary Columns : For doing summary calculations such as summations etc.
Place holder Columns : These columns are useful for storing the value in a variable
2) Can u have more than one layout in report
It is possible to have more than one layout in a report by using the additional layout option in the layout editor.
3) Can u run the report with out a parameter form
Yes it is possible to run the report without parameter form by setting the PARAM value to Null
4) What is the lock option in reports layout
By using the lock option we cannot move the fields in the layout editor outside the frame. This is useful for maintaining the fields .
5) What is Flex
Flex is the property of moving the related fields together by setting the flex property on
6) What are the minimum number of groups required for a matrix report
The minimum of groups required for a matrix report are 4
Important Questions in Oracle, Developer /2000(Form 4.5 and Reports 2.5)
Oracle
1) What are the Back ground processes in Oracle and what are they.
1) This is one of the most frequently asked question.There are basically 9 Processes but in a
general system we need to mention the first five background processes.They do the house keeping
activities for the Oracle and are common in any system.
The various background processes in oracle are
a) Data Base Writer(DBWR) :: Data Base Writer Writes Modified blocks from Database buffer cache to Data Files.This is required since the data is not written whenever a transaction is commited.
b)LogWriter(LGWR) :: LogWriter writes the redo log entries to disk. Redo Log data is generated in redo log buffer of SGA. As transaction commits and log buffer fills, LGWR writes log entries into a online redo log file.
c) System Monitor(SMON) :: The System Monitor performs instance recovery at instance startup.This is useful for recovery from system failure
d)Process Monitor(PMON) :: The Process Monitor peforms process recovery when user Process fails. Pmon Clears and Frees resources that process was using.
e) CheckPoint(CKPT) :: At Specified times, all modified database buffers in SGA are written to data files by DBWR at Checkpoints and Updating all data files and control files of database to indicate the
most recent checkpoint
f)Archieves(ARCH) :: The Archiver copies online redo log files to archival storal when they are busy.
g) Recoveror(RECO) :: The Recoveror is used to resolve the distributed transaction in network
h) Dispatcher (Dnnn) :: The Dispatcher is useful in Multi Threaded Architecture
i) Lckn :: We can have upto 10 lock processes for inter instance locking in parallel sql.
2) How many types of Sql Statements are there in Oracle
2) There are basically 6 types of sql statments.They are
a) Data Defination Language(DDL) :: The DDL statments define and maintain objects and drop objects.
b) Data Manipulation Language(DML) :: The DML statments manipulate database data.
c) Transaction Control Statements :: Manage change by DML
d) Session Control :: Used to control the properties of current session enabling and disabling roles and changing .e.g :: Alter Statements,Set Role
e) System Control Statements :: Change Properties of Oracle Instance .e.g:: Alter System
f) Embedded Sql :: Incorporate DDL,DML and T.C.S in Programming Language.e.g:: Using the Sql Statements in languages such as 'C', Open,Fetch, execute and close
3) What is a Transaction in Oracle
3) A transaction is a Logical unit of work that compromises one or more SQL Statements executed by a single User. According to ANSI, a transaction begins with first executable statment and ends when it is explicitly commited or rolled back.
4) Key Words Used in Oracle
4) The Key words that are used in Oracle are ::
a) Commiting :: A transaction is said to be commited when the transaction makes permanent changes resulting from the SQL statements.
b) Rollback :: A transaction that retracts any of the changes resulting from SQL statements in Transaction.
c) SavePoint :: For long transactions that contain many SQL statements, intermediate markers or savepoints are declared. Savepoints can be used to divide a transactino into smaller points.
d) Rolling Forward :: Process of applying redo log during recovery is called rolling forward.
e) Cursor :: A cursor is a handle ( name or a pointer) for the memory associated with a specific stament. A cursor is basically an area allocated by Oracle for executing the Sql Statement. Oracle uses an implicit cursor statement for Single row query and Uses Explcit cursor for a multi row query.
f) System Global Area(SGA) :: The SGA is a shared memory region allocated by the Oracle that contains Data and control information for one Oracle Instance.It consists of Database Buffer Cache and Redo log Buffer.
g) Program Global Area (PGA) :: The PGA is a memory buffer that contains data and control information for server process.
g) Database Buffer Cache :: Databese Buffer of SGA stores the most recently used blocks of datatbase data.The set of database buffers in an instance is called Database Buffer Cache.
h) Redo log Buffer :: Redo log Buffer of SGA stores all the redo log entries.
i) Redo Log Files :: Redo log files are set of files that protect altered database data in memory that has not been written to Data Files. They are basically used for backup when a database crashes.
j) Process :: A Process is a 'thread of control' or mechansim in Operating System that executes series of steps.
5) What are Procedure, functions and Packages
5) Procedures and functions consist of set of PL/SQL statements that are grouped together as a unit to solve a specific problem or perform set of related tasks.
Procedures do not return values while Functions return only One Value
Packages :: Packages Provide a method of encapsulating and storing related procedures, functions, variables and other Package Contents
6) What are Database Triggers and Stored Procedures
6) Database Triggers :: Database Triggers are Procedures that are automatically executed as a result of insert in, update to, or delete from table.
Database triggers have the values old and new to denote the old value in the table before it is deleted and the new indicated the new value that will be used. DT are useful for implementing complex business rules which cannot be enforced using the integrity rules.We can have the trigger as Before trigger or After Trigger and at Statement or Row level.
e.g:: operations insert,update ,delete 3
before ,after 3*2 A total of 6 combinatons
At statment level(once for the trigger) or row level( for every execution ) 6 * 2 A total of 12.
Thus a total of 12 combinations are there and the restriction of usage of 12 triggers has been lifted from Oracle 7.3 Onwards.
Stored Procedures :: Stored Procedures are Procedures that are stored in Compiled form in the database.The advantage of using the stored procedures is that many users can use the same procedure in compiled and ready to use format.
7) How many Integrity Rules are there and what are they
7) There are Three Integrity Rules. They are as follows ::
a) Entity Integrity Rule :: The Entity Integrity Rule enforces that the Primary key cannot be Null
b) Foreign Key Integrity Rule :: The FKIR denotes that the relationship between the foreign key and the primary key has to be enforced.When there is data in Child Tables the Master tables cannot be deleted.
c) Business Integrity Rules :: The Third Intigrity rule is about the complex business processes which cannot be implemented by the above 2 rules.
8) What are the Various Master and Detail Relation ships.
8) The various Master and Detail Relationship are
a) NonIsolated :: The Master cannot be deleted when a child is exisiting
b) Isolated :: The Master can be deleted when the child is exisiting
c) Cascading :: The child gets deleted when the Master is deleted.
9) What are the Various Block Coordination Properties
9) The various Block Coordination Properties are
a) Immediate
Default Setting. The Detail records are shown when the Master Record are shown.
b) Deffered with Auto Query
Oracle Forms defer fetching the detail records until the operator navigates to the detail block.
c) Deffered with No Auto Query
The operator must navigate to the detail block and explicitly execute a query
10) What are the Different Optimisation Techniques
10) The Various Optimisation techniques are
a) Execute Plan :: we can see the plan of the query and change it accordingly based on the indexes
b) Optimizer_hint:
set_item_property('DeptBlock',OPTIMIZER_HINT,'FIRST_ROWS');
Select /*+ First_Rows */ Deptno,Dname,Loc,Rowid from dept
where (Deptno > 25)
c) Optimize_Sql ::
By setting the Optimize_Sql = No, Oracle Forms assigns a single cursor for all SQL statements.This slow downs the processing because for evertime the SQL must be parsed whenver they are executed.
f45run module = my_firstform userid = scott/tiger optimize_sql = No
d) Optimize_Tp ::
By setting the Optimize_Tp= No, Oracle Forms assigns seperate cursor only for each query SELECT statement. All other SQL statements reuse the cursor.
f45run module = my_firstform userid = scott/tiger optimize_Tp = No
11) How do u implement the If statement in the Select Statement
11) We can implement the if statement in the select statement by using the Decode statement.
e.g select DECODE (EMP_CAT,'1','First','2','Second'Null);
Here the Null is the else statement where null is done .
12)How many types of Exceptions are there
12) There are 2 types of exceptions. They are
a) System Exceptions
e.g. When no_data_found, When too_many_rows
b) User Defined Exceptions
e.g. My_exception exception
When My_exception then
13) What are the inline and the precompiler directives
13) The inline and precompiler directives detect the values directly
14) How do you use the same lov for 2 columns
14) We can use the same lov for 2 columns by passing the return values in global values and using the global values in the code
15) How many minimum groups are required for a matrix report
15) The minimum number of groups in matrix report are 4
16) What is the difference between static and dynamic lov
16) The static lov contains the predetermined values while the dynamic lov contains values that come at run time
17) What are snapshots and views
17) Snapshots are mirror or replicas of tables. Views are built using the columns from one or more tables. The Single Table View can be updated but the view with multi table cannot be updated
18) What are the OOPS concepts in Oracle.
18) Oracle does implement the OOPS concepts. The best example is the Property Classes. We can categorise the properties by setting the visual attributes and then attach the property classes for the
objects. OOPS supports the concepts of objects and classes and we can consider the peroperty classes as classes and the items as objects
19) What is the difference between candidate key, unique key and primary key
19) Candidate keys are the columns in the table that could be the primary keys and the primary key
is the key that has been selected to identify the rows. Unique key is also useful for identifying the distinct rows in the table.
20)What is concurrency
20) Cuncurrency is allowing simultaneous access of same data by different users. Locks useful for accesing the database are
a) Exclusive
The exclusive lock is useful for locking the row when an insert,update or delete is being done.This lock should not be applied when we do only select from the row.
b) Share lock
We can do the table as Share_Lock as many share_locks can be put on the same resource.
21) Previleges and Grants
21) Previleges are the right to execute a particulare type of SQL statements.
e.g :: Right to Connect, Right to create, Right to resource
Grants are given to the objects so that the object might be accessed accordingly.The grant has to be
given by the owner of the object.
22)Table Space,Data Files,Parameter File, Control Files
22)Table Space :: The table space is useful for storing the data in the database.When a database is created two table spaces are created.
a) System Table space :: This data file stores all the tables related to the system and dba tables
b) User Table space :: This data file stores all the user related tables
We should have seperate table spaces for storing the tables and indexes so that the access is fast.
Data Files :: Every Oracle Data Base has one or more physical data files.They store the data for the database.Every datafile is associated with only one database.Once the Data file is created the size cannot change.To increase the size of the database to store more data we have to add data file.
Parameter Files :: Parameter file is needed to start an instance.A parameter file contains the list of instance configuration parameters e.g.::
db_block_buffers = 500
db_name = ORA7
db_domain = u.s.acme lang
Control Files :: Control files record the physical structure of the data files and redo log files
They contain the Db name, name and location of dbs, data files ,redo log files and time stamp.
23) Physical Storage of the Data
23) The finest level of granularity of the data base are the data blocks.
Data Block :: One Data Block correspond to specific number of physical database space
Extent :: Extent is the number of specific number of contigious data blocks.
Segments :: Set of Extents allocated for Extents. There are three types of Segments
a) Data Segment :: Non Clustered Table has data segment data of every table is stored in
cluster data segment
b) Index Segment :: Each Index has index segment that stores data
c) Roll Back Segment :: Temporarily store 'undo' information
24) What are the Pct Free and Pct Used
24) Pct Free is used to denote the percentage of the free space that is to be left when creating a table. Similarly Pct Used is used to denote the percentage of the used space that is to be used when creating a table
eg.:: Pctfree 20, Pctused 40
25) What is Row Chaining
25) The data of a row in a table may not be able to fit the same data block.Data for row is stored in a chain of data blocks .
26) What is a 2 Phase Commit
26) Two Phase commit is used in distributed data base systems. This is useful to maintain the integrity of the database so that all the users see the same values. It contains DML statements or Remote Procedural calls that reference a remote object. There are basically 2 phases in a 2 phase commit.
a) Prepare Phase :: Global coordinator asks participants to prepare
b) Commit Phase :: Commit all participants to coordinator to Prepared, Read only or abort Reply
27) What is the difference between deleting and truncating of tables
27) Deleting a table will not remove the rows from the table but entry is there in the database dictionary and it can be retrieved But truncating a table deletes it completely and it cannot be retrieved.
28) What are mutating tables
28) When a table is in state of transition it is said to be mutating. eg :: If a row has been deleted then the table is said to be mutating and no operations can be done on the table except select.
29) What are Codd Rules
29) Codd Rules describe the ideal nature of a RDBMS. No RDBMS satisfies all the 12 codd rules and Oracle Satisfies 11 of the 12 rules and is the only Rdbms to satisfy the maximum number of rules.
30) What is Normalisation
30) Normalization is the process of organizing the tables to remove the redundancy. There are mainly 5 Normalization rules.
a) 1 Normal Form :: A table is said to be in 1st Normal Form when the attributes are atomic
b) 2 Normal Form :: A table is said to be in 2nd Normal Form when all the candidate keys are dependant on the primary key
c) 3rd Normal Form :: A table is said to be third Normal form when it is not dependant transitively
31) What is the Difference between a post query and a pre query
31) A post query will fire for every row that is fetched but the pre query will fire only once.
32) Deleting the Duplicate rows in the table
32) We can delete the duplicate rows in the table by using the Rowid
33) Can U disable database trigger? How?
33) Yes. With respect to table
ALTER TABLE TABLE
[[ DISABLE all_trigger ]]
34) What is pseudo columns ? Name them?
34) A pseudocolumn behaves like a table column, but is not actually
stored in the table. You can select from pseudocolumns, but you
cannot insert, update, or delete their values. This section
describes these pseudocolumns:
* CURRVAL
* NEXTVAL
* LEVEL
* ROWID
* ROWNUM
35) How many columns can table have?
The number of columns in a table can range from 1 to 254.
36) Is space acquired in blocks or extents ?
In extents .
37) what is clustered index?
In an indexed cluster, rows are stored together based on their cluster key values .
Can not applied for HASH.
38) what are the datatypes supported By oracle (INTERNAL)?
Varchar2, Number,Char , MLSLABEL.
39 ) What are attributes of cursor?
%FOUND , %NOTFOUND , %ISOPEN,%ROWCOUNT
40) Can you use select in FROM clause of SQL select ?
Yes.
Forms 4.5 Questions
1) Which trigger are created when master -detail rela?
1) master delete property
* NON-ISOLATED (default)
a) on check delete master
b) on clear details
c) on populate details
* ISOLATED
a) on clear details
b) on populate details
* CASCADE
a) per-delete
b) on clear details
c) on populate details
2) which system variables can be set by users?
2)
SYSTEM.MESSAGE_LEVEL
SYSTEM.DATE_THRESHOLD
SYSTEM.EFFECTIVE_DATE
SYSTEM.SUPPRESS_WORKING
3) What are object group?
3)
An object group is a container for a group of objects. You define an object group when you want to package related objects so you can copy or reference them in another module.
4) What are referenced objects?
4)
Referencing allows you to create objects that inherit their functionality and appearance from other objects.
Referencing an object is similar to copying an object, except that the resulting reference object maintains a
link to its source object. A reference object automatically inherits any changes that have been made to the
source object when you open or regenerate the module that contains the reference object.
5) Can you store objects in library?
5)
Referencing allows you to create objects that inherit their functionality and appearance from other
objects. Referencing an object is similar to copying an object, except that the resulting reference
object maintains a link to its source object. A reference object automatically inherits any changes that
have been made to the source object when you open or regenerate the module that contains the
reference object.
6) Is forms 4.5 object oriented tool ? why?
6)
yes , partially. 1) PROPERTY CLASS - inheritance property
2) OVERLOADING : procedures and functions.
7) Can you issue DDL in forms?
7)
yes, but you have to use FORMS_DDL.
Referencing allows you to create objects that inherit their functionality and appearance from other
objects. Referencing an object is similar to copying an object, except that the resulting reference object
maintains a link to its source object. A reference object automatically inherits any changes that have
been made to the source object when you open or regenerate the module that contains the reference object.
Any string expression up to 32K:
¡Pa literal
¡P an expression or a variable representing the text of a block of dynamically created PL/SQL code
¡P a DML statement or
¡P a DDL statement
Restrictions:
The statement you pass to FORMS_DDL may not contain bind variable references in the string, but the
values of bind variables can be concatenated into the string before passing the result to FORMS_DDL.
8) What is SECURE property?
8)- Hides characters that the operator types into the text item. This setting is typically used for
password protection.
9 ) What are the types of triggers and how the sequence of firing in text item
9)
Triggers can be classified as Key Triggers, Mouse Triggers ,Navigational Triggers.
Key Triggers :: Key Triggers are fired as a result of Key action.e.g :: Key-next-field, Key-up,Key-Down
Mouse Triggers :: Mouse Triggers are fired as a result of the mouse navigation.e.g. When-mouse-button-presed,when-mouse-doubleclicked,etc
Navigational Triggers :: These Triggers are fired as a result of Navigation. E.g : Post-Text-item,Pre-text-item.
We also have event triggers like when ¡Vnew-form-instance and when-new-block-instance.
We cannot call restricted procedures like go_to(¡¥my_block.first_item¡¦) in the Navigational triggers
But can use them in the Key-next-item.
The Difference between Key-next and Post-Text is an very important question. The key-next is fired as a result of the key action while the post text is fired as a result of the mouse movement. Key next will not fire unless there is a key event.
The sequence of firing in a text item are as follows ::
a) pre - text
b) when new item
c) key-next
d) when validate
e) post text
10 ) Can you store pictures in database? How?
10)Yes , in long Raw datatype.
11) What are property classes ? Can property classes have trigger?
11) Property class inheritance is a powerful feature that allows you to quickly define objects that conform to
your own interface and functionality standards. Property classes also allow you to make global changes to
applications quickly. By simply changing the definition of a property class, you can change the definition
of all objects that inherit properties from that class.
Yes . All type of triggers .
* 12 a) If you have property class attached to an item and you have same trigger written for the item .
Which will fire first?
12)Item level trigger fires , If item level trigger fires, property level trigger won't fire. Triggers at the lowest level are always given the first preference. The item level trigger fires first and then the block and then the Form level trigger.
13) What are record groups ? * Can record groups created at run-time?
13)A record group is an internal Oracle Forms data structure that has a column/row framework similar to a
database table. However, unlike database tables, record groups are separate objects that belong to the
form module in which they are defined. A record group can have an unlimited number of columns of type
CHAR, LONG, NUMBER, or DATE provided that the total number of columns does not exceed 64K.
Record group column names cannot exceed 30 characters.
Programmatically, record groups can be used whenever the functionality offered by a two-dimensional
array of multiple data types is desirable.
TYPES OF RECORD GROUP:
Query Record Group A query record group is a record group that has an associated SELECT statement.
The columns in a query record group derive their default names, data types, and lengths from the database columns referenced in the SELECT statement. The records in a query record group are the rows retrieved by the query associated with that record group.
Non-query Record Group A non-query record group is a group that does not have an associated query, but whose structure and values can be modified programmatically at runtime.
Static Record Group A static record group is not associated with a query; rather, you define its
Structure and row values at design time, and they remain fixed at runtime.
14) What are ALERT?
14)An ALERT is a modal window that displays a message notifying operator of some application
Condition.
15) Can a button have icon and label at the same time ?
15) -NO
16) What is mouse navigate property of button?
16)
When Mouse Navigate is True (the default), Oracle Forms performs standard navigation to move the focus
to the item when the operator activates the item with the mouse.
When Mouse Navigate is set to False, Oracle Forms does not perform navigation (and the resulting validation) to move to the item when an operator activates the item with the mouse.
17) What is FORMS_MDI_WINDOW?
17) forms run inside the MDI application window. This property is useful for calling a form from another one.
18) What are timers ? when when-timer-expired does not fire?
18) The When-Timer-Expired trigger can not fire during trigger, navigation, or transaction processing.
19 ) Can object group have a block?
19)Yes , object group can have block as well as program units.
20) How many types of canvases are there.
20)There are 4 types of canvases called as Content and Stack Canvas. Content canvas is the default and the one that is used mostly for giving the base effect. Its like a plate on which we add items and stacked canvas is used for giving 3 dimensional effect.
The following questions might not be asked in an Average Interview and could be asked when the Interviewer wants to trouble u and go deeppppppppppppp¡K¡KHe cannot go further¡K..
1) What are user-exits?
1) It invokes 3GL programs.
2) Can you pass values to-and-fro from foreign function ? how ?
2) Yes . You obtain a return value from a foreign function by assigning the return value to an Oracle Forms
variable or item. Make sure that the Oracle Forms variable or item is the same data type as the return value
from the foreign function.
After assigning an Oracle Forms variable or item value to a PL/SQL variable, pass the PL/SQL variable as
a parameter value in the PL/SQL interface of the foreign function. The PL/SQL variable that is passed as
a parameter must be a valid PL/SQL data type; it must also be the appropriate parameter type as defined
in the PL/SQL interface.
3) What is IAPXTB structure ?
3) The entries of Pro * C and user exits and the form which simulate the proc or user_exit are stored in IAPXTB table in d/b.
4) Can you call WIN-SDK thruo' user exits?
4) YES.
5) Does user exits supports DLL on MSWINDOWS ?
5) YES .
6) What is path setting for DLL?
6) Make sure you include the name of the DLL in the FORMS45_USEREXIT variable of the ORACLE.INI file, or rename the DLL to F45XTB.DLL. If you rename the DLL to F45XTB.DLL, replace the existing F45XTB.DLL in the ORAWINBIN directory with the new F45XTB.DLL.
7) How is mapping of name of DLL and function done?
7) The dll can be created using the Visual C++ / Visual Basic Tools and then the dll is put in the
path that is defined the registery.
8) what is precompiler?
8) It is similar to C precompiler directives.
9) Can you connect to non - oracle datasource ? How?
9) Yes .
10 ) what are key-mode and locking mode properties? level ?
10) Key Mode : Specifies how oracle forms uniquely identifies rows in the database.This is property includes
for application that will run against NON-ORACLE datasources .
Key setting unique (default.)
dateable
n-updateable.
Locking mode :
Specifies when Oracle Forms should attempt to obtain database locks on rows that correspond to queried records in the form.
a) immediate b) delayed
11) What are savepoint mode and cursor mode properties ? level?
11) Specifies whether Oracle Forms should issue savepoints during a session. This property is included primarily for applications that will run against non-ORACLE data sources. For applications that will run against ORACLE, use the default setting.
Cursor mode - define cursur state across transaction
Open/close.
12) Can you replace default form processing ? How ?
13) What is transactional trigger property?
13) Identifies a block as transactional control block. i.e. non - database block that oracle forms should manage as transactional block.(NON-ORACLE datasource) default - FALSE.
14) What is OLE automation ?
14) OLE automation allows an OLE server application to expose a set of commands and functions that can be
invoked from an OLE container application. OLE automation provides a way for an OLE container application to use the features of an OLE server application to manipulate an OLE object from the OLE container environment. (FORMS_OLE)
15) What does invoke built-in do?
15) This procedure invokes a method.
Syntax:
PROCEDURE OLE2.INVOKE
(object obj_type,
method VARCHAR2,
list list_type := 0);
Parameters:
object Is an OLE2 Automation Object.
method Is a method (procedure) of the OLE2 object.
list Is the name of an argument list assigned to the OLE2.CREATE_ARGLIST function.
16) What are OPEN_FORM,CALL_FORM,NEW_FORM? diff?
16) CALL_FORM : It calls the other form. but parent remains active, when called form completes the operation , it releases lock and control goes back to the calling form.
When you call a form, Oracle Forms issues a savepoint for the called form. If the CLEAR_FORM function
causes a rollback when the called form is current, Oracle Forms rolls back uncommitted changes to this
savepoint.
OPEN_FORM : When you call a form, Oracle Forms issues a savepoint for the called form. If the
CLEAR_FORM function causes a rollback when the called form is current, Oracle Forms rolls back
uncommitted changes to this savepoint.
NEW_FORM : Exits the current form and enters the indicated form. The calling form is terminated as
the parent form. If the calling form had been called by a higher form, Oracle Forms keeps the higher call
active and treats it as a call to the new form. Oracle Forms releases memory (such as database cursors)
that the terminated form was using.
Oracle Forms runs the new form with the same Runform options as the parent form. If the parent form was
a called form, Oracle Forms runs the new form with the same options as the parent form.
17 ) What is call form stack?
17) When successive forms are loaded via the CALL_FORM procedure, the resulting module hierarchy is known as the call form stack.
18) Can u port applictions across the platforms? how?
18) Yes we can port applications across platforms.Consider the form developed in a windows system.The form would be generated in unix system by using f45gen my_form.fmb scott/tiger
GUI
1) What is a visual attribute?
1) Visual attributes are the font, color, and pattern properties that you set for form and menu objects that appear in your application's interface.
2) Diff. between VAT and Property Class? imp
2)Named visual attributes define only font, color, and pattern attributes; property classes can contain these and any other properties.
You can change the appearance of objects at runtime by changing the named visual attribute
programmatically; property class assignment cannot be changed programmatically.
When an object is inheriting from both a property class and a named visual attribute, the named visual
attribute settings take precedence, and any visual attribute properties in the class are ignored.
3 ) Which trigger related to mouse?
3) When-Mouse-Click
When-Mouse-DoubleClick
When-Mouse-Down
When-Mouse-Enter
When-Mouse-Leave
When-Mouse-Move
When-Mouse-Up
4) What is Current record attribute property?
4) Specifies the named visual attribute used when an item is part of the current record.
Current Record Attribute is frequently used at the block level to display the current row in a multi-record
If you define an item-level Current Record Attribute, you can display a pre-determined item in a special color
when it is part of the current record, but you cannot dynamically highlight the current item, as the input focus changes.
5) Can u change VAT at run time?
5) Yes. You can programmatically change an object's named visual attribute setting to change the font, color,
and pattern of the object at runtime.
6) Can u set default font in forms?
6) Yes. Change windows registry(regedit). Set form45_font to the desired font.
7) Can u have OLE objects in forms?
7) Yes.
8) Can u have VBX and OCX controls in forms ?
8) Yes.
9) What r the types of windows (Window style)?
9) Specifies whether the window is a Document window or a Dialog window.
10) What is OLE Activation style property?
10) Specifies the event that will activate the OLE containing item.
11) Can u change the mouse pointer ? How?
11) Yes. Specifies the mouse cursor style. Use this property to dynamically change the shape of the cursor.
Reports 2.5
1) How many types of columns are there and what are they
1) Formula columns :: For doing mathematical calculations and returning one value
Summary Columns :: For doing summary calculations such as summations etc.
Place holder Columns :: These columns are useful for storing the value in a variable
2) Can u have more than one layout in report
2) It is possible to have more than one layout in a report by using the additional layout option in the layout editor.
3) Can u run the report with out a parameter form
3) Yes it is possible to run the report without parameter form by setting the PARAM value to Null
4) What is the lock option in reports layout
4) By using the lock option we cannot move the fields in the layout editor outside the frame. This is useful for maintaining the fields .
5) What is Flex
5) Flex is the property of moving the related fields together by setting the flex property on
6) What are the minimum number of groups required for a matrix report
6) The minimum of groups required for a matrix report are 4
3.0 Data Base Administration
3.1 Introduction to DBA
1. What is a database instance ? Explain
A database instance (server) is a set of memory structures and background processes that access a set of database files.
The process can be shared by all users.
The memory structures that are used to store most queried data from database. This helps us to improve database performance by decreasing the amount of I/O performed against data file.
2. What is parallel server?
Multiple instances accessing the same database (Only in Multi-CPU environments).
3. What is Schema ?
The set of objects owned by user account is called the schema
4. What is an Index ? How it is implemented in Oracle Database ?
An index is a database structure used by the server to have direct access of a row in a table.
An index is automatically created when a unique or primary key constraint clause is specified in create table command (Ver 7.0)
5. What is clustres ?
Group of tables physically stored together because they share common columns and are often used together is called Clusters.
6. What is a cluster key ?
The related columns of the tables are called the cluster key. The cluster key is indexed using a cluster index and its value is stores only once for multiple tables in the cluster.
7. What are the basic element of Base configuration of an oracle Database ?
It consists of
one or more data files
one or more control files
two or more redo log files
The database contains
Multiple users/schemas
one or more rollback segments
one or more tablespaces
Data dictionary tables
User objects (tables,indexes,views etc)
The server that access the database consists of
SGA (Database buffer, Dictionary Cache Buffers, redo log buffers,Shared SQL pool)
SMON
PMON
LGWR
DBWR
ARCH
CKPT
RECO
Dispatcher
User process with associated PGA
8. What is deadlock ? Explain.
Two processes waiting to update the rows of a table which are locked by the other process then deadlock arises.
In a database environment this will often happen because of not issuing proper row lock commands. Poor design of front-end application may cause this situation and the performance of server will reduce drastically.
These locks will be released automatically when a commit/rollback operation performed or any one of this processes being killed externally.
3.2 Memory Management
9. What is SGA ? How it is different from Ver 6 and Ver 7 ?
The System Global Area in a Oracle database is the area in memory to facilitates the transfer of information between users. It holds the most recently requested structural information about the database.
The structure is Database buffers, Dictionary Cache, Redo Log Buffer and Shared SQL pool (Ver 7) area.
10. What is Shared SQL pool ?
The data dictionary cache is stored in an area in SGA called the Shared SQL Pool. This will allow sharing of parsed SQL statements among concurrent users.
11. What is meant by Program Global Area (PGA) ?
It is area in memory that is used by a Single Oracle User process.
12. What is a data segment ?
Data segment are the physical areas within a database block in which the data associated with tables and clusters are stored.
13. What are the factors causing the reparsing of SQL statements in SGA ?
Due to insufficient Shared SQL pool size
Monitor the ratio of the reloads takes place while executing SQL statements. If the ratio is greater that 1 then increase the SHARED_POOL_SIZE.
3.3 Logical & Physical Architecture of Database
14. What is Database Buffers ?
Database buffers are cache in the SGA used to hold the data blocks that are read from the data segments in the database such as tables, indexes and clusters. DB_BLOCK_BUFFERS parameter in INIT.ORA decides the size.
15. What is dictionary cache ?
Dictionary cache is information about the database objects stored in a data dictionary table.
16. What is meant by recursive hits ?
Number of times processes repeatedly query the dictionary table is called recursive hits. It is due to the data dictionary cache is too small. By increasing the SHARED_POOL_SIZE parameter we can optimize the size of Data Dictionary Cache.
17. What is meant by redo log buffer ?
Changes made to entries are written to the on-line redo log files so that they can be used in roll forward operation during database recoveries. Before writing them into the redo log files, they will first brought to redo log buffers in SGA and LGWR will write into files frequently. LOG_BUFFER parameter will decide the size.
18. How will you swap objects into a different table space for an existing database ?
Export the user
Perform import using the command imp system/manager file=export.dp indexfile=newfile.sql. This will create all definitions into newfile.sql.
Drop necessary objects.
Run the script newfile.sql after altering the tablespaces.
Import from the backup for the necessary objects.
19. List the Optimal Flexible Architecture (OFA) of Oracle database ? or
How can we organise the tablespaces in Oracle database to have maximum performance ?
SYSTEM - Data dictionary tables
DATA - Standard operational tables
DATA2 - Static tables used for standard operations
INDEXES - Indexes for Standard operational tables
INDEXES1 - Indexes of static tables used for standard operations
TOOLS - Tool table
TOOLS1 - Indexes for tools table
RBS - Standard Operations Rollback Segments
RBS1,RBS2 - Additional/Special rollback segments
TEMP - Temporary purpose tablespace
TEMP_USER - Temporary tablespace for users
USERS - User tablespaces.
20. How will you force database to use particular rollback segment ?
SET TRANSACTION USE ROLLBACK SEGMENT rbs_name
21. What is meant by free extent ?
A free extent is a collection of continuous free blocks in tablespace. When a segment is dropped its extents are reallocated and are marked as free.
22. How free extents are managed in Ver 6 and Ver 7. ?
Free extents cannot be merged together in Ver 6.0
Free extents are periodically coalesces with the neighboring free extent Ver 7.0.
23. Which parameter in Storage clause will reduce no of rows per block ?
PCTFREE parameter
Row size also reduces no of rows per block.
24. What is significance of having storage clause ?
We can plan the storage for a table as how much initial extents are required, how much can be extended next, how much % should leave free for managing row updations etc.
25. How does space allocation take place within a block ?
Each block contains entries as follows :
Fixed block header
Variable block header
Row header, row date (Multiple rows may exists)
PCTFREE (% of free space for row updation in future)
26. What is the role of PCTFREE parameter is Storage clause ?
This is used to reserve certain amount of space in a block for expansion of rows.
27. What is the OPTIMAL parameter ?
It is used to set the optimal length of rollback segment.
28. What is the functionality of SYSTEM tablespace ?
To manage the database level of transactions such as modifications of the data dictionary table that record information about the free space usage.
29. How will you create multiple rollback segments in a database ?
Create a database which implicitly creates a SYSTEM Rollback Segment in a SYSTEM tablespace.
Create a Second Rollback Segment name R0 in the SYSTEM tablespace.
Make new rollback segment available (After shutdown, modify init.ora file and Start database)
Create other tablespace (RBS) for rollback segments.
Create additional Rollback segment in tablespace (RBS)
Deactivate Rollback Segment R0 and activate the newly created rollback segments.
30. How the space utilisation takes place within rollback segments ?
It will try to fit the transaction in a cyclic fashion to all existing extents. Once it found an extent is in use then it forced to acquire a new extent. (No of extents is based on the OPTIMAL size).
31. Why query fails sometimes ?
Rollback segment dynamically extent to handle larger transactions entry loads.
A single transaction may wipeout all available free space in the Rollback Segment Tablespace. This prevents other user using Rollback segment.
32. How will you monitor the space allocation ?
By querying DBA_SEGMENT table/View
33. How will you monitor rollback segment status ?
Querying the DBA_ROLLBACK_SEGS view
The status available as follows :
IN USE - Rollback Segment is on-line
AVAILABLE - Rollback Segment available bur not on-line
OFF-LINE - Rollback Segment us off-line
INVALID - Rollback Segment dropped
NEEDS RECOVERY - Contains data but need recovery or corrupted
PARTLY AVAILABLE - Contains data from an unresolved transaction involving a distributed database
34. List the sequence of events when a large transaction that exceeds beyond its optimal value when an entry wraps and causes the rollback segment to expand into another extend.
Transaction Begins
An entry is made in the RBS header for new transactions entry
Transaction acquired blocks in an extent of RBS
The entry attempts to wrap into second extent. None is available. So that the RBS must extent.
The RBS checks to see if it is oldest inactive segment
Oldest inactive segment is eliminated
RBS extends
The Data dictionary table for space management are updated
Transaction Completes.
35. How can we plan storage for very large tables ?
Limit the number of extents in the table
Separate the Table from its indexes
Allocate sufficient temporary storage
36. How will you estimate the space required by non-clustered tables ?
Calculate the total block header size
Calculate the available data space per block
Calculate the combined column length of the average row
Calculate the total average row size
Calculate the average number rows that can fit in a block
Calculate the number of blocks and bytes required for the table
After arriving the calculation add the additional space to calculate the initial extent size for working area
37. Is it possible to use raw devices as data file and what is the advantages over file system files ?
Yes.
The advantages over file system files :
I/O will be improved because Oracle is bye-passing the kernal while writing into disk.
Disk Corruption will be very less.
38. What is a control file ?
Database's overall physical architecture is maintained in a file called control file. It will be used to maintain internal consistency and guide recovery operations. Multiple copies of control files are advisable.
39. How to implement the multiple control files for an existing database ?
Shutdown the database
Copy one of the existing control file to new location'
Edit config.ora file by adding new control file name
Restart the database
40. What is meant by Redo Log file mirroring ? How it can be achieved ?
Process of having a copy of redo log files is called mirroring.
This can be achieved by creating group of log files together, so that LGWR will automatically writes them to all the members of the current on-line redo log group. If any one group fails then database automatically switch over to next group.
41. What is advantage of having disk shadowing/Mirroring ?
Shadow set of disks save as a backup in the event of disk failure. In most Operating System if any disk failure occurs it automatically switchover to place of failed disk.
Improved performance because of most OS support volume shadowing can direct file I/O request to use the shadow set of files instead of the main set of files. This reduces I/O load on the main set of disks.
42. What is use of rollback segment in Database ?
They allow the database to maintain read consistency between multiple transactions.
43. What is a Rollback segment entry ?
It is the set of before image data blocks that contain rows that are modified by a transaction.
Each Rollback Segment entry must be completed within one rollback segment.
A single rollback segment can have multiple rollback segment entries.
44. What a hit ratio ?
It is a measure of well the data cache buffer is handling requests for data.
Hit Ratio = (Logical Reads - Physical reads - Hit Misses) / Logical reads.
45. When will be a segment released ?
When Segment is dropped.
When Shrink (RBS only)
When truncated (TRUNCATE used with drop storage option)
46. What are disadvantages of having raw devices ?
We should depend on export/import utility for backup/recovery (fully reliable)
The tar command cannot be used for physical file backup, instead we can use dd command which is less flexible and has limited recoveries.
47. List the factors that can affect the accuracy of the estimations ?
The space used transaction entries and deleted records does not become free immediately after completion due to delayed cleanout.
Trailing nulls and length bytes are not stored.
Inserts of, updates to, and deletes of rows as well as columns larger than a single data block, can cause fragmentation and chained row pieces.
3.4 Database Security & Administration
48. What is user account in Oracle database ?
An user account is not a physical structure in Database but it is having important relationship to the objects in the database and will be having certain privileges.
49. How will you enforce security using stores procedures ?
Don't grant user access directly to tables within application
Instead grant the ability to access the procedures that access the tables
When procedure executed it will execute the privilege of procedures owner. Users cannot access tables except via the procedure.
50. What are the dictionary tables used to monitor a database spaces ?
DBA_FREE_SPACE
DBA_SEGMENTS
DBA_DATA_FILES
51. What are responsibilities of a Database Administrator ?
1. Installing and upgrading the Oracle Server and application tools
2. Allocating system storage and planning future storage requirements for the database system.
3. Managing primary database structures(tablespaces)
4. Managing primary objects (table,views,indexes)
5. Enrolling users and maintaining system security
6. Ensuring compliance with Oracle license agreement
7. Controlling and monitoring user access to the database
8. Monitoring and optimising the performance of the database
9. Planning for backup and recovery of database information
10. Maintain archived data on tape
11. Backing up and restoring the database
12. Contacting Oracle Corporation for technical support
52. What are requirements one should fulfill to connect to ORACLE as internal?
Operating system account has the operating system privileges that allow you to connect
One should be authorised to connect as internal
Database has a password for internal connections, and you know the password must use a dedicated server
53. What are the roles and user accounts created automatically with the database ?
DBA role - Contains all database system privileges
SYS user account - The DBA role will be assigned to this account. All of the base tables and views for the database's dictionary are store in this schema and are manipulated only by ORACLE.
SYSTEM user account - It has all the system privileges for the database and additional tables and views that display administrative information and internal tables and views used by oracle tools are created using the username.
54. What are the database administrators utilities available ?
SQL*DBA - This allows DBA to monitor and control an ORACLE database.
SQL*Loader - It loads data from standard operating system files (Flat files) into ORACLE database tables.
EXPORT(exp) and IMPOER (imp) utilities allow you to move existing data in ORACLE format to and from ORACLE database.
55. What are the minimum parameters should exist in the parameter file (init.ora) ?
DB_NAME - Must set to a text string of not more that 8 characters and it will be stored inside the datafiles, redo log files and control file while database creation.
DB_DOMAIN - It is string that specifies the network domain where the database is created. The global database name is identified by setting these parameters (DB_NAME & DB_DOMAIN)
CONTROL_FILES - List of control filenames of the database. If name is not mentioned then default name will be used.
DB_BLOCK_SIZE - The default data block size and is operating system dependent. It cannot be changed after database creation except by re-creating the database.
DB_BLOCK_BUFFERS - The maximum number of operating system processes that can be connected to ORACLE concurrently. The value should be 5 (background process) and additional 1 for each user.
ROLLBACK_SEGMENTS - List of rollback segments an ORACLE instance acquires at database startup.
Also optionally LICENSE_MAX_SESSIONS,LICENSE_SESSION_WARNING and LICENSE_MAX_USERS.
56. What is a trace file and how it is created ?
Each server and background process can write an associated trace file. When an internal error is detected by a process or user process, it dumps information about the error to its trace. This can be used for tuning the database.
57. What are roles ? How can we implement roles ?
Roles are easiest way to grant and manage common privileges needed by different groups of database users.
Creating roles and assigning privies to roles.
Assign each role to group of users. This will simplify the job of assigning privileges to individual users.
58. What are the steps to switch a database's archiving mode between NOARCHIEVELOG and ARCHIVELOG mode ?
1. Shutdown the database instance
2. Backup the database
3. Perform any operating system specific steps (optional)
4. Start up a new instance and mount but do not open the database
5. Switch the database's archiving mode.
59. How can you enable automatic archiving ?
Shut the database
Backup the database
Modify/Include LOG_ARCHIVE_START = TRUE in init.ora file
Start up the database
60. How can we specify the Archived log file name format and destination ?
By setting the following values in init.ora file
LOG_ARCHIVE_FORMAT = arch%S/s/T/t.arc (%S - Log sequence number and is zero left-paded, %s - Log sequence number not paded, %T - Thread number left-zero-paded and %t - Thread number not paded). The file name created is arch0001.arc %S is used.
LOG_ARCHIEVE_DEST = path
Shut the database and change these parameters in init.ora files.
61. What is the user of ANALYZE command ?
To perform one of these function on an index, table, or cluster :
to collect statistics about object used by the optimizer and store them in the data dictionary.
to delete statistics about the object from the data dictionary
to validate the structure of the object
to identify migrated and chained rows of the table or cluster.
3.5 Managing Distributed Databases
62. How can we reduce the network traffic ?
Replication of data in distributed environment
Using snapshots to replicate data
Using remote procedure calls.
63. What is a snapshot ?
Snapshot is an object used to dynamically replicate data between distributed databases at specified time intervals. In ver 7.0 they are read only.
64. What are the various type of snapshots ?
Simple and Complex.
65. Differentiative simple and complex, snapshots
A simple snapshot is based on a query that does not contains GROUP BY clauses, CONNECT by clauses, JOINs, Subquery or a set of operations.
A complex snapshots contain at least any one of the above.
66. What is dynamic data replication ?
Updating or inserting records in remote database through database triggers. It may fail if remote database is having any problem.
67. How can you enforce referential integrity in snapshots ?
Time the references to occur when master tables are not in use.
Perform the references manually immediately after locking the master tables.
We can join tables in snapshots by creating a complex snapshot that will be based on the master tables.
68. What are the options available to refresh snapshots ?
COMPLETE - Tables are completely regenerated using the snapshot's query and the master tables every time the snapshot referenced.
FAST - If simple snapshot used then a snapshot log can be used to send only the changes to the snapshot tables.
FORCE - The default value. If possible it performs a FAST refresh; Otherwise it will perform a COMPLETE refresh.
69. What is a snapshot tag ?
It is a table that maintains a record of modifications to the master table in a snapshot. It is stored in the same database as master table and is only available for simple snapshots. It should be created before creating snapshots.
70. When will the data in the snapshot log be used ?
The data in the snapshot log is used during fast references of the table's snapshots.
71. What are the pre-requisites to create a snapshot log ?
We must be able to create a after row trigger on table (i.e. it should not be already available)
After giving table previleges.
We cannot specify snapshot log name because oracle uses the name of the master table in the name of the database objects that support its snapshot log.
The master table name should be less than or equal to 23 characters.
(The table name created will be MLOG$_tablename, and trigger name will be TLOG$_tablename)
72. What are the benefits of distributed options in databases ?
Database on other servers can be updated and those transactions can be grouped together with others in a logical unit.
Database uses a two phase commit
73. What is a two-phase commit ?
Database on other servers can be updated and those transactions can be grouped together with others in a logical unit is called two-phase commit. They are
The Preparation Phase : An initiating node called the global coordinator notifies all sites involved in the transaction to be ready either commit or rollback the transaction.
The Commit Phase : If there is no problem with prepare phase, then all sites commit their transactions. If a network or node failure occurs, then all sites rollback their transactions.
3.6 Managing Backup & Recovery
74. What are the different methods of backing up oracle database ?
Logical Backups
Cold Backups
Hot Backups (Archive log)
75. What is a logical backup ?
Logical backup involves reading a set of database records and writing them into a file. Export utility is used for taking backup and Import utility is used to recover from backup.
76. What is cold backup ? What are the elements of it ?
Cold backup is taking backup of all physical files after normal shutdown of database. We need to take
All Data files
All Control files
All on-line redo log files
Then init.ora file (optional)
77. What are the different kind of export backups ?
Full backup - Complete database
Incremental Backup - Only affected tables from last incremental date / Full backup date
Cumulative backup - Only affected table from the last cumulative date / Full backup date
78. What is hot backup and how it can be taken ?
Taking backup of archive log files when database is open. For this the ARCHIVELOG mode should be enabled. The following files need to be backed up :
All data files
All archive log, redo log files
On control file.
79. What is the use of FILE option in EXP command ?
To give the export file name.
80. What is the use of COMPRESS option in EXP command ?
Flag to indicate whether export should compress fragmented segments into single extents.
81. What is the use of GRANT option in EXP command ?
A flag to indicate whether grants on database objects will be exported or not. Values is 'Y' or 'N'.
82. What is the use of INDEXES option in EXP command ?
A flag to indicate whether indexes on tables will be exported.
83. What is use of ROWS option in EXP command ?
Flag to indicate whether table rows should be exported. If 'N' only DDL statements for the database objects will be created.
84. What is the use of CONSTRAINTS option in EXP command ?
A flag to indicate whether constraints on table need to be exported.
85. What is the use of FULL option in EXP command ?
A flag to indicate whether full database export should be performed.
86. What is the use of OWNER option in EXP command ?
List of table accounts should be exported.
87. What is the use of TABLES option in EXP command ?
List of tables should be exported.
88. What is use of RECORD LENGTH option in EXP command ?
Record length in bytes.
89. What is use of INCTYPE option in EXP command ?
Type export should be performed. COMPLETE, CUMULATIVE, INCREMENTAL
90. What is use of RECORD option in EXP command ?
For incremental exports, the flag indicates whether a record will be stored in data dictionary tables recording the export.
91. What is the use of PARFILE option in EXP command ?
Name of the parameter file to passed for export.
92. What is the use of ANALYSE (Ver 7) option in EXP command ?
A flag to indicate whether statistical information about the exported objects should be written to export dump file.
93. What is use of CONSISTENT (Ver 7) option in EXP command ?
A flag to indicate whether a read consistent version of all the exported objects should be maintained.
94. What is the use of Log (Ver 7) option in EXP command ?
The name of file to which log of the export will be written.
95. What is use of FILE option in IMP command ?
The name of file from which import should be performed.
96. What is the use of SHOW option in IMP command ?
A flag to indicate whether file content should be displayed or not.
97. What is the use of IGNORE option in IMP command ?
A flag to indicate whether import should ignore errors encounter when issuing CREATE command.
98. What is the use of GRANT option in IMP command ?
A flag to indicate whether grants on database objects will be imported.
99. What is use of INDEXES option in IMP command ?
A flag to indicate whether import should import index on tables or not.
100. What is use of ROWS option in IMP command ?
A flag to indicate whether rows should be imported. I f this is set to 'N' then only DDL for the database objects will be executed ?
101. What is the use of FULL option in IMP command ?
A flag to indicate whether full import should be done or not.
102. What is the use of FROMUSER option in IMP command ?
A list of database accounts whose objects should be read from the export dump file.
103. What is use of TOUSER option in IMP command ?
A list of database accounts into which objects in the export dump file will be imported
104. What is use of TABLES option in IMP command ?
A list of tables to be imported.
105. What is use of RECORDLENGTH option in IMP command ?
The length of the record in bytes of the export dump file.
106. What is use of INCTYPE option in the IMP command ?
The type of import being performed.
107. What is use of COMMIT option in IMP command ?
A flag to indicate whether import should commit after each array. If 'N' then commit will take place at table level
108. What is use of PARFILE option in IMP command ?
Name of the parameter file to passed for import command.
109. What is use of INDEXFILE option in IMP command ?
If filename is given then all the DDL will be created in the given file.
110. What is use of DESTROY (Ver 7) option in IMP command ?
A flag to indicate whether the create tablespace command found in dump files from full exports will be executed.
111. What is use of LOG option in IMP command ?
Name of the file to which the log of the import will be written.
112. Consider a case below : User is taking the backup in the following fashion :
Type F I I I I C I I I I C I I
Date 1 2 3 4 5 6 7 8 9 10 11 12 13
F - Full Backup
I - Incremental Backup
C - Cumulative Backup
Suppose database crash on 14th morning. How can we retrieve the database ?
Create the database
Import from the Full backup which was taken on 1st
Import from Cumulative backups which was taken on 6th
Import from Cumulative backups which was taken on 1th
Import from the Incremental backups 12,13 respectively.
Now the database will be available to latest status provided there is no transaction taken place after the 13th incremental backup.
113. List the steps to restore the database if data file lost. (Assume we are taking hot backups)
Copy the lost file from the backup to the original location
Start the instance
Mount the database
Recover the database using recover database command
Open the database
114. What are the points to be taken care when we are using SQL*Loader for importing data from flat files ?
Whether table and indexes are properly sized.
Direct option being used or not (Ver 7)
If one time load do not create any index until data has been loaded and table size is verified.
115. What are the advantages of using direct path option in SQL*Loader ?
It bypasses the normal processing of insert statements and instead writes directly to tables data blocks.
When direct option is used index become invalid and once the load complete the new key is merged with all old one and bring the status to valid.
Data should be presorted otherwise it needs the double the size in tablespace.
116. What are areas a DBA can monitor the database using SQLDBA command?
DBA can monitor the following areas to do fine tuning of the database :
Processes
Sessions
Tables(Locks etc)
SQL Area
Library Cache
Latch
Locks
File I/O
System I/O
Rollback Segments
Statistics (System, Sessions)
Apart from this all DBA activities can be performed through SQLDBA command.
DDE ¡V OLE
DDE - Dynamic Data Exchange.
DLL - Dynamic Link Library
OLE - Object Linking and Embedding.
MAPI ¡V Messaging Application Program Interface
What is DDE ?
DDE is method for Inter Process Communication. An inter process communication is a method of passing data between processes and synchronising events.
How does DDE work ?
DDE uses shared memory to exchange data and a protocol to synchronize passing of data.
What does a DLL contain ?
A DLL contains code, data and windows resources.
How does a DLL work ?
A DLL allocates a global memory block to an application and uses this to exchange data with application.
What are the two types of DDE application ?
Message based DDE applications and Dynamic Data Exchange Management Library application.
What are the parts of a DDE application ?
Client application, Server application, Client/Server application and Monitor application.
What is a monitor application in the context of DDE ?
A monitor application can only intercept messages but cannot act on it.
What is the use of a monitor application ?
A monitor application can be used as a debugging tool.
What is the connection between OLE and DDE ?
OLE is a set of DDE executable commands to which DDE protocol is applicable.
What is the difference between an embedded object and a linked object ?
An embedded object is stored in the document itself while the document just stores a reference to the linked object.
If a link object is changed independently of the document, wht happens the linked object in the document ?
1. The reference object is automatically refreshed
2. The reference object is not refreshed
3. The user decides whether the object is to refreshed or if the older version is retained.
Answer is 2
What are the types of OLE applications ?
Client, Server and Object handlers.
What is an object handler ?
An Object handler is a set of DLL that facilitate communication between client application and server application.
What are the advantages of OLE ?
No need to switch between applications. Facilitate the use of specialized applications to create objects which can be embedded.
What is the difference between a stored procedure and a database trigger ?
A trigger is automatically executed when the firing event occurs while stored procedure has to be invoked.
Oracle Forms:
1. How to use single data block to query multiple tables
2. How to see the select statement when we issue execute_query
3. What are the system variables can be changed
4. How do you trap default forms processing ( DML)
5. What is the difference between post-query and post-select
6. What is purpose and order of firing the following triggers
1. on fetch
2. on select
7. What is the number of records buffered and Query array size properties of data block
8. What is the difference between object libraries and object groups
9. What is the difference between pre-query and pre-select triggers
10. What is the difference between pre-text-item and when-new-item-instance triggers
11. What is the order of firing the following triggers
1. when-new-form-instance
2. pre-text-item
(Both are in form-level)
12. What is the validation unit property of form module
13. What is the order of checking for a program unit from form module(local program unit, library, stored procedure)
14. What is the difference between PL/SQL library and object library
15. what is the use of pre text/pre record/pre form
16. types of record groups and usage
17. what is id_null function
18. what is the return data types of id_null, show_alert, show_lov
19. what is the difference between call_form , open_form, new_form
Which is restricted built-in and why?
Which can¡¦t issue savepoint
What is session parameter of open_form?
20. which are the triggers will fire in the following situation
I have three text items
1. Text-item1
1.key-next-item
Go_item (¡¥text_item2¡¦);
Go_item (¡¥text_item3¡¦);
2. Text-item2
1. Pre-text-item
2. When-validate-item
3. When-new-item-instance
4. Key-next-item
5. Post-text-item
6. Post-change
3. Text-item3
1. Pre-text-item
2. When-validate-item
3. When-new-item-instance
4. Key-next-item
5. Post-text-item
6. Post-change
If I press tab or enter key at text-item1 what are the triggers will fire and order of firing during the entire navigation.
If I change key-next-item trigger of text-item1
Go_item (¡¥text_item2¡¦);
: Text_item2: = ¡¥Nagendra¡¦;
Go_item (¡¥text_item3¡¦);
Then what are the triggers will fire and order of firing
21. What is synchronous and asynchronous parameters for run_product built-in
22. How do you suppress the logon screen while running the form for the first time
23. What is primary canvas property of window and where it will be useful
24. I have when-button-pressed trigger at form , block and item level
If I want to execute first block, form then item level trigger what changes I have to make.
25. what is data parameter and text parameter
26. Can we re-generate a library that is currently accessing by some other session
27. Can we re-generate and save a library that has been attached with some forms but they are running currently.
28. Can we re-generate a library that has been attached with some forms , will the changes will reflect in the referenced forms
29. What is the use of transactional triggers
30. Can we modify a sub classed object ( from object group and from object libraries)
31. How to set forms default directory
32. What is the return data type of populate_group built-in
33. What is the difference between OLE object created at design time and runtime
34. Will the timer will expire during large query executing
35. What is the built-in package available to manipulate text files( forms)
36. Can we define a relation between two control blocks
37. If we change relation property from non-isolated to cascading what changes will occur
38. What is the coordination property of a relation
39. If we delete on-clear-details trigger in a relation what happens
40. What is the first trigger fires when we run a form
41. What is the use of enforce primary key property of data block
42. Can we put items other than buttons in the toolbars
43. Which object relates content and stacked canvases(window)
44. How to navigate from one form to other form(built-in)
45. How to copy values from list item to record group
46. In a non-isolated relation what is the order of firing the following triggers
1. on-populate-details
2. on-clear-details
3. pre-query
4. pre-select
47. How to find out the previous form id in multi form application(it¡¦s system variable)
48. How to use single LOV for multiple items
Oracle reports:
1. Minimum requirement to make a matrix report
(Queries, Groups and Repeating frames)
2. How to change the font of an field at runtime based on the value
3. What is the anchoring and enclosing object
4. What is anchor object
5. How to rotate a field( data base field in the layout)
6. What is the difference between lexical and bind parameters
7. What is the place holder
8. What is the use of frame(not repeating)
9. What is the use of format triggers
10. SRW package
11. What is flex mode and confine mode
12. what difference between the logical and physical pages and planes
13. what is the use of group filter
SQL and PL/SQL
1. Queries for Nth maximum ,Nth row
2. what is use of the index ( maximum try to cover)
3. Select the departments whose sum of the salary greater than the sum of salaries of any department?
4. What is implicit cursors
5. What is public synonyms and uses
6. When index will be used in the query
7. What is the result of the following queries
1. Select * from emp where Comm in (null);
2. Select * from emp where Comm = null;
3. Select * from emp where Comm = ¡¥¡¦;
4. Select * from emp where Comm is ( select null from dual);
8. Query to display employee name and his managers name
9. Query to find the employees who is having more then one subordinate
10. Query to find the employees whose salary is greater then his department average salary
11. Query to display employees salary as 2000 for department 20 and rest as their salaries
12. Query to display no of employees in the department 10, 20,30 in a single row
Output
Dept10 dept20 dept30
2 5 6
13. Query to find the no of subordinate levels for given manager
14. Query to find the no of employees who is drawing less than 1500 and greater than 2000
Server concepts
1. what are the physical database components
2. what are the logical database components
3. what is row chaining
4. what is the relation between oracle data block ,extents and segments
5. how many types of segments are there
6. what is temporary segments
7. what is redo log
8. what is the difference between rollback segments and redo log files
9. what is the difference between database buffers and redo log buffer of SGA
10.
1) How delete duplicate records in a table
delete from emp where rowid not in (select max(rowid) from emp group by empno);
2) How to make a column into not null column.
Ans: alter table emp
modify (empno not null); ->this can be done only when all the values in empno are non null (i.e not empty)
„h To make a not null column into null column
alter table emp
modify (empno null);
The fallowing are the rules for
i. adding null or not null property
>You may change a column¡¦s null property to not null only when that field does contain null values(i. It can¡¦t be empty)
>At any time you may change a column¡¦s not null property to null
ii. adding a colum to a table
>You may add a column at any time if NOT NULL isn¡¦t specified (i.e when new column can accept null values )
>You may add a NOT NULL column in three steps.
a. Add the column without NOT NULL specified.
b. Fill every row in that column with data.
c. Modify the column to be NOT NULL.
iii. modifying a column
>You can increase a CHAR column¡¥s width at any time.
>You can increase the number of digits and the number of decimal places in a NUMBER column at any time
>To CHANGE data types or to DECREASE column¡¦s width the column should be null for every row
3)Write queries for the fallowing
ex. select * from emp_self;
EMP_NO EMPN_NAME SAL MGR DEPTID
--------- -------------------- ---------- ---------- ----------
400 jane 20000 110 20
102 Mary 19000 110 20
101 charles 8000 105 50
104 Linda 9000 100 10
110 john 25000 105 20
105 newton 2000 50
100 ALEN 15000 105 50
200 BORIS 3000 110 20
103 DAVID 10000 100 10
300 monica 7000 105 50
i) Query to get the employees who are working under mgr with salary > 10000
select emp_no,mgr from emp_self where mgr in (select emp_no from emp_self where sal > 10000);
ii) Query to get the employees who are getting salaries more than their managers
select a.emp_no from emp_self a,emp_self b where a.mgr =b.emp_no and a.sal > b.sal;
EMP_NO
-------
101
100
110
300
iii) Query to find the nth highest salary
select a.empn_name,a.sal from emp_self a where &n = (select count(*) from emp_self b where a.sal < b.sal);
When n=1 , sal =20000 ->second highest salary ; n=4 , sal =10000 ->fifth highest salary ;
iv) Query to find the second highest salary in different departments.
select a.deptid,min(a. sal) from emp_self a where 1 in (select count(*) from emp_self b
where a.sal < b.sal group by b.deptid) group by a.deptid;
DEPTID MIN(A.SAL)
------- ----------
10 9000
20 20000
50 8000
v) Query to find departments with total salary >25000
select deptid from emp_self having sum(sal) >25000 group by deptid;
DEPTID
------
20
50
4) study the fallowing pl/sql block and find the type of error ->syntax,semantic(logical) or precedence
begin
for i in 1..5 loop
update emp
set sal = 1000 where empno =100 ;
end loop;
end;
5) Difference between (MAX,MIN) and (GREATEST ,LEAST)
The functions max and min compares different rows . Whereas greatest and least work on a group of columns ,either actual or calculated values within a single row.
Ex. select * from emp_self;
EMP_NO EMPN_NAME SAL MGR
------ -------------------- ------- ----------
100 alen 9,000 105
200 boris 10,000 110
101 charles 8,000 105
SQL> select max(sal),min(sal) from emp_self;
MAX(SAL) MIN(SAL)
---------- ----------
10000 8000
SQL> select greatest(sal),least(sal) from emp_self;
GREATEST(SAL) LEAST(SAL)
------------- ----------
9000 9000
10000 10000
8000 8000
6)Different kinds of constraints .
6)Where Procedures,Functions and Triggers are stored ?.
7)What are the improtant differences between Procedures,Functions and Triggers ?.
8)Can we call a Procedure from a Trigger ?.
9)what are packages ?.
9)What are the different kinds of parameters ?.
10)Can we return a OUT parameter from a procedure ?.
11)Differences between ROWNUM and ROWID .
12)How do you handle exceptions ?.
12)How many system defined exceptions are there ?.
13)How do you write user defined message for all the system defined exceptions.
14)Difference between Commit and H(?)ost .
15)Differences between delete ,truncate and drop commands .
16) How do you display messages in the backend procedure ?.
17) why can¡¦t you use create/drop while declaring a trigger ?.
18)Advantages of union over joins .
19)Definitions of commit, rollback, save point
20)Difference between truncate and delete (truncate =delete + commit)
1)Name the five global report triggers
i. before report
ii. after report
iii. between pages
iv. before parameter form
v.after parameter form
As a general rule, any processing that will affect the data retrieved by the report should be performed in the Before Parameter Form or After Parameter Form triggers. (These are the two report triggers that fire before anything is parsed or fetched.) Any processing that will not affect the data retrieved by the report can be performed in the other triggers.
Report Builder has five global report triggers. You cannot create new global report triggers. The trigger names indicate at what point the trigger fires:
Before Report Fires before the report is executed but after queries are parsed.
After Report Fires after you exit the Previewer, or after report output is sent to a specified destination, such as a file, a printer, or an Oracle Office userid. This trigger can be used to clean up any initial processing that was done, such as deleting tables. Note, however, that this trigger always fires, whether or not your report completed successfully.
Between Pages Fires before each page of the report is formatted, except the very first page. This trigger can be used for customized page formatting. In the Previewer, this trigger only fires the first time that you go to a page. If you subsequently return to the page, the trigger does not fire again.
Before Parameter Form Fires before the Runtime Parameter Form is displayed. From this trigger, you can access and change the values of parameters, PL/SQL global variables, and report-level columns. If the Runtime Parameter Form is suppressed, this trigger still fires. Consequently, you can use this trigger for validation of command line parameters.
After Parameter Form Fires after the Runtime Parameter Form is displayed. From this trigger, you can access parameters and check their values. This trigger can also be used to change parameter values or, if an error occurs, return to the Runtime Parameter Form. Columns from the data model are not accessible from this trigger. If the Runtime Parameter Form is suppressed, the After Parameter Form trigger still fires. Consequently, you can use this trigger for validation of command line parameters or other data.
2) Name the different types of alerts
note , stop ,caution
3)call_form ( ), new_form ( )
call_form ( ) :-Runs an indicated form while keeping the parent form active. Form Builder runs the called form with the same Runform preferences as the parent form. When the called form is exited Form Builder processing resumes in the calling form at the point from which you initiated the call to CALL_FORM.
PROCEDURE CALL_FORM
(formmodule_name VARCHAR2);
New_form( ) :-
Exits the current form and enters the indicated form. The calling form is terminated as the parent form. If the calling form had been called by a higher form, Form Builder keeps the higher call active and treats it as a call to the new form. Form Builder releases memory (such as database cursors) that the terminated form was using.
Form Builder runs the new form with the same Runform options as the parent form. If the parent form was a called form, Form Builder runs the new form with the same options as the parent form.
PROCEDURE NEW_FORM
(formmodule_name VARCHAR2);
4) system.mode->
SYSTEM.MODE indicates whether the form is in Normal, Enter Query, or Fetch Processing mode. The value is always a character string.
NORMAL Indicates that the form is currently in normal processing mode.
ENTER-QUERY Indicates that the form is currently in Enter Query mode.
QUERY Indicates that the form is currently in fetch processing mode, meaning that a query is currently being processed.
Usage Notes
When using SYSTEM.MODE to check whether the current block is in Enter Query mode, be aware that if testing from a When-Button-Pressed trigger in a control block, Enter Query mode will never be entered, because the control block is not the current block.
4)What are important new(Advanced) features of Forms 6.0.
5)Different types of list boxes.
6)What are record groups ?.
7)In case of a block with multiple records how to display records on the screen without using cursors ?.
8)Can we access a row in the first block from second by referencing block name along with the rowid ?.
9)In case of a block with multiple records how do check where a user entering a duplicate record well before saving it ?.
10)How to take care of concurrency ?.
9.0 Forms 4.5
9.1 Object Groups
1. What is an object group ?
An object group is a container for a group of obects. You define an object group when you want to package related objects, so that you can copy or reference them in another module.
2. What are the different objects that you cannot copy or
reference in object groups ?
Objects of different modules
Another Objects group
Individual block depndent objects
Program Units.
9.2 Canvas Views
3. What are different types of canvas views ?
There are four types of canvas views :
Content canvas views
Stacked canvas views
Horizontal tool bar
Vertical tool bar
4. Explain about Content Canvas Views
Most canvas views are Content-Canvas Views. It is the base view that occupies the entire content pane of the window in which it is displayed.
5. Explain about Stacked Canvas Views ?
A stacked canvas view is displayed in a window on top of, or ¡§stacked¡¨ on the content canvas view assigned to that same window. Stacked canvas view obscure some part of the underlying content-canvas view, and are often shown and hidden programmatically.
6. Explain about Horizontal/Vertical toolbar Canvas-Views ?
Toolbar canvas-views are used to create toolbar for individual windows. Horizontal toolbars are displayed at the top a window, just under the menubar. Vertical toolbars are displayed along the leftside of a window.
7. Name the functions used to get/set the canvas properties ?
get_view_property, set_view_property.
9.3 Windows
8. What is the relation between windows and Canvas Views ?
Canvas-Views are the background objects on which you place the interface items(text items, check boxes, radio groups etc.,) and boilerplate objects(boxes,lines,images, etc.,) that operators interact with as they run your form. Each canvas-view is displayed in a window.
9. What are the Different Modals of Windows ?
There are Two different modals of Windows are
Modeless Windows
Modal Windows
10. What are Modeless Windows ?
More than one modeless windows can be displayed at the same time, and operators can navigate among them if your application allows them to do so. On most GUI platforms, modeless windows can also be layered to appear either in front of or behind other windows.
11. What are Modal Windows ?
Modal windows are usually used as dialogs, and have restricted funtionality compared to modeless windows. On some platforms,for example, operators cannot resize, scroll, or iconify a modal window.
12. How do you display console on a window ?
The console includes the status line and message line, and is displayed at the bottom of the window to which it is assigned.
To specify that the console should be displayed, set the console window form property to the name of any window in the form, To hide the console, set the console window to <Null>
13. What is the Remove on Exit property ?
For a modeless window, it determines whether Oracle Forms hides the window automatically, when the operator navigates to an item in another window.
14. How many windows in a form can have Console ?
Only one window in a form can display the console, and you cannot change the console assignment at runtime.
15. Can you have more than one content canvas view attached
with a window?
Yes. Each window you create must have at least one content canvas-view assigned to it. You can also create a window that has multiple content canvas-views. At runtime, only one of the content canvas-views assigned to a window is displayed at a time.
16. What are the different Window Events activated at Runtime ?
When-Window-Activated
When-Window_Closed
When-Window_Deactivated
When_Window_Resized
Within these triggers, you can examine the build-in system variable SYSTEM.EVENT_WINDOW to determine the name of the window for which the trigger fired
9.4 Modules
17. What are the different types of Modules available in Oracle
Forms ?
There are three types of modules in Oralcle Forms :
Form Module - A collection of objects and code routines
Menu Module - A collection of Menus( a main menu and any number of submenu objects) and menu item commands that together make up an application menu.
Library Module - A collection of user-named procedures,functions, and packages that can be called from other modules in the application.
18. What are the default extensions of the files created by Forms
Module ?
.FMB Form Module Binary
.FMX Form Module Executable
19. What are the default extensions of the files created by Menu
Module ?
.MMB Menu Module Binary
.MMX Menu Module Executable
20. What are the default extensions of the files created by
Library Module ?
.PLL PL/SQL Library Module Binary
9.5 Master - Detail
21. What is Master Detail Relationship ?
A Master-detail relationship is an association between two base table blocks - a master block and a detail block. The relationship between the blocks reflects a primary key to foreign key relationship between the tables on which the blocks are based.
22. What is coordination Event?
Any event that makes a different record in themaster block the current record is a coordination-causing event.
23. What are the two phases of block coordination?
There are two phases of block coordination; the clear phase and the population phase. During the clear phase, Oracle forms navigates internally to the detail block and flushes the obsolete detail records. During the population phase, oracle forms issues a SELECT statement to repopulate the details block with the detail records associated with the new master record. These operations are accomblished through the execution og triggers.
24. what are most common types of complex master_detail
relationship?
There are three most common types of complex master-detail relationships:
master with dependent details
master with independent details
detail with two masters
25. What arethe different types of Delete details we can establish
in Master-Details?
Cascade
Isolate
Non-Isolate
26. What are the different default triggers created when Master
Deletes Property is set to Non-isolated?
Master Deletes Property Resulting Triggers
Non-Isolated (the default) On-Check-Delete-Master
On-Clear-Details
On-Populate-Details
27. What are the different default triggers created when Master
Deletes Property is set to Cascade?
Master Deletes Property Resulting Triggers
Cascading On-Clear-Details
On-Populate-Details
Pre-Delete
28. What are the different default triggers created when Master
Deletes Property is set to Isolated?
Master Deletes Property Resulting Triggers
Isolated On-Clear-Details
On-Populate-Details
29. What are the Coordination properties ina master detai
relationship?
The coordinatio in properties are
Deferred
Auto-Query
These properties determine when the population phase of block coordination should occur.
30. What are the different types of coordinations of the Master
with the Detail block?
Coordination of the detail block with its master can be
Immediate
Deferred with Auto-Query
Deferred with the no Auto-Query
31. what is the immediate coordination of the Master with the
Detail block?
Immediate(Deferred False, Auto-Querry False) The default settings.
When a coordination-causing event occurs, the detail records are fetched immediately.
32. What is the deferred with Auto-Quey Coordination of the
Master with the Detail block?
Deferred with Auto-Query(Deferred True,Auto-Query true) When a Coordination-causing events occurs,Oracle Forms defers fetching the associated detail records until the operator navigates to the detail block.
33 . What is the Deferred with no Auto-Query Coordination of
the Master with the Detail block?
Deferred with Auto-Query(Deferred True,Auto-Query False) When a Coordination-causing events occurs,Oracle Forms doesn¡¦t automatically fetch the detail records the operator must navigate to the detail block and explicitly execute a query.
34. What is an Alert?
An Alert is a modal Window that displays a message notifying the operator of some application condition.
35. When do you use Alert?
Use alerts to advise operators of unusual situations or to warn operators who are about to perform an action that might have undesirable or unexpected consequences.
36 . what are the different display styles of alert?
Find_alert
Show_alert
37 . How do you change the alert message during runtime?
You can change an alert message at run time by executing the SET_ALERT_PROPERTY built-in procedure. Changing an alert¡¦s message allows you to reuse the same alert object, but display a different message each time it is invoked.
Example
Set_Alert_Property(alert_id,ALERT_MESSAGE_TEXT,¡¦The product you selected is not in stock¡¦);
Editors
38 . What are the different types of editors?
There are three editors that can be used at run time the default editor, a system editor,or a
user-named editor.
39 . What is the default editor?
The default editor provides standard editing features,including search/replace and cut,copy and paste. The default editor is built into every form and is automatically available from every
text item.
40. What is the System Editor?
If there is a system editor available, you can specify that Oracle Forms should use the current system editor, rather than the default editor.
41 . What is the User named Editor?
A User named Editor has the same text editing functionality has the default editor, but, because it is a named object,you can specify editor attributes such as window display size,position,and title.
42 . What are the built-ins to display the user-named editor?
A User-named editor can be displayed programatically with built in procedure SHOW_EDITOR,EDIT_TEXTITEM independent of any particular text item.
43 . What is the difference between SHOW_EDITOR and
EDIT_TEXTITEM?
Show_Editor is the generic built-in which accepts any editor name and takes some input string and returns modified output string. whereas the edit_textitem built_in needs the input focus to be in the textitem before the built_in is executed.
LOV(List Of Values)
44. What is an LOV?
An LOV is a scrollable popup window that provides the operator with either a single or multi-column selection list.
45. What is the basic data structure that is required for creating
an LOV?
Record Group
46. What is the ¡§LOV for validation¡¨ Property of an item? What is
the use of it?
When LOV for validation is set to true, Oracle Forms compares the current value of the text item to the values in the first column displayed in the LOV whenever the validation event occurs.
If the value in the text item matches one of the values in the first column of the LOV, Validation succeeds ,The LOV is not displayed, the processing continues normally.
If the value in the text item doesn¡¦t match one of the values in the first column of the LOV,Oracle Forms displays the LOV and uses the text item value as the search criteria to automatically reduce the list.
47. What are the built-ins used to display the LOV?
Show_lov
list_values
47. What are the built-ins that are used to attach an LOV
programatically to an item?
Set_item_property
Get_item_property
(by setting the LOV_NAMEproperty)
48. What are the built-ins that are used for setting the LOV
properties at runtime?
get_lov_property
set_lov_property
Record Groups
49. What is the Record Group?
A record group is an internal Oracle Forms data structure that has a column/row framework similar to a database table. However, unlike database tables,record groups are separate objects that bekong to the form module in which they are defined.
50. How many number of columns a record group can have?
A record group can have an ultimate number of columns of type CHAR,LONG,NUMBER, and DATE provided that the total number of columns does not exceed 64k.
51 . What is the maximum allowed length of a Record Group
Column?
Record group column names cannot exceed 30 characters.
52. What are the different types of Record Group?
Query Record Groups
NonQuery Record Groups
Static Record Groups
53. What is a Query Record Group?
A Query record is a record group that has an associated SELECTstatement. The columns in a query record group derive their default names,datatypes and lengths from the database columns referenced in the SELECT statement. The records in a query record group are the rows retreived by the query associated with that record group.
54 . What is a Non Query Record Group?
A non-query record group is a group that does not have an associated query,but whose structures can be modified programatically at runtime.
55. What is a Static Record Group?
A Static record group is not associated with a query,rather, you define its structure and row values at design time, and they remain fixed at runtime.
56 . What are the built-ins used for creating and deleting
groups?
CREATE_GROUP(function)
CREATE_GROUP_FROM_QUERY(function)
DELETE_GROUP(Procedure)
57. What are the built-ins used for modifying a group structure?
ADD_GROUP_COLUMN(function)
ADD_GROUP_ROW(Procedure)
DELETE_GROUP_ROW(Procedure)
POPULATE_GROUP(function)
POPULATE_GROUP_WITH_QUERY(function)
SET_GROUP_CHAR_CELL(Procedure)
SET_GROUP_DATE_CELL(Procedure)
SET_GROUP_NUMBER_CELL(Procedure)
58 . What are the built-ins used for getting cell values?
GET_GROUP_CHAR_CELL(function)
GET_GROUP_DATE_CELL(function)
GET_GROUP_NUMBER_CELL(function)
59 . What are the built-ins used for processing rows?
GET_GROUP_ROW_COUNT(function)
GET_GROUP_SELECTION(function)
GET_GROUP_SELECTION(function)
RESET_GROUP_SELECTION(Procedure)
SET_GROUP_SELECTION(Procedure)
UNSET_GROUP_SELECTION(Procedure)
60. What are the built-ins used for finding Object ID functions?
FIND_GROUP(function)
FIND_COLUMN(function)
61. Use the ADD_GROUP_COLUMN function to add a column to
a record group that was created at design time
(1) True (2) False.
False
62. Use the Add_Group_row procedure to add a row to a static
record group.(1)True (2) False
False
PARAMETERS
63. What are the Parameters?
Parameters provide a simple mechanism for defining and setting the values of inputs that are required by a form at startup. Form parameters are variables of type CHAR,NUMBER, or
DATE that you define at design time.
64 . What are the Built-ins used for sending Parameters to
forms?
You can pass parameter values to a form when an application executes the CALL_FORM,NEW_FORM,OPEN_FORM,or RUN_PRODUCT.
65 . What is the maximum number of characters the parameter
can store?
The maximum number of characters the parameter can store is only valid for CHAR parameters, which can be up to 64k. Number parameters default to 23 bytes and DATE parameters default to 7 bytes.
66 . How do you call other ORACLE products from Oracle
Forms?
RUN_PRODUCT is a built-in used to invoke one of the supported Oracle tools products and specifies the name of the document or module to be run. If the called product is unavailable at the time of calkl, Oracle Forms returns a message to the operator.
67. How do you reference a Parameter?
In PL/SQL, you can reference and set the values of form parameters using bind variable syntax.
Example
:PARAMETER.parameter_name=¡¦VIKRAM¡¦; or
:block.item=PARAMETER.parameter_name;
68 . How do you reference a parameter indirectly?
To indirectly reference a parameter
Use the NAME_IN and COPY built-ins to indirectly set and reference the parameter¡¦s value.
Example:
Name_In(¡¥PARAMETER.my_param¡¦)
Copy(¡¥SURESH¡¦,¡¦PARAMETER>my_param¡¦)
69 . What are the difference Parameter Types?
Text Parameters
Data Parameters
70 . When do you use DATA_PARAMETER type?
When the value of a data parameter being passed to a called product is always the name of a record group defined in the current form. Data paremeters are used to pass data to products invoked with the RUN_PRODUCT built-in subprogram.
71 . Can you pass data parameters to forms?
No.
Images
72. What are the different types of images?
BoilerPlate Images
Image Items
73 . What is the difference between Boilerplate images and
image items?
Boilerplate Images BoilerPlate images are static images(either vector or bitmap) that you import from the file system or database to use as graphical elements in your form, such as company logos and maps.
Image ItemsImage items are special types of interfaace controls that store and display either vector or bitmaps images. Like other items that store values, image items can be either base table items (items that relate directly to database columns) or control items. The definiton of an image item is storred as part of the form module. .FMB and .FMX files, but no image file is actually assciated with an image item until the item is populated at runtime.
74 . What are the triggers associated with the image items?
The Following triggers are available for responding programatically to image items events
When-Image-Activated
First when the operator double-clicks on a image item
When-Image_Pressed
Fires when an operator clicks or double-clicks on an image item
75. What is the use of IMAGE_ZOOM built_in?
You can use the IMAGE_ZOOM built-in subprogram to manipulate images in image items.
Working with Multiple Forms
76. How do you create a new session while opening a new form?
Using OPEN_FORM built-in setting the SESSION option.
Ex: OPEN_FORM(¡§STOCKS¡¦,ACTIVE,SESSION);
When you invoke multiple forms with OPEN_FORM and CALL_FORM in the
Same application,state whether the following are TRUE or FALSE
77 . Any attempt to navigate programatically to a disabled form
in a call form stack is allowed
FALSE
78 . An open form cannot execute the CALL_FORM procedure if
a chain of called forms has been initiated by another open
form
TRUE
79. When a form is invoked with CALL_FORM, does Oracle
Forms issues a savepoint? TRUE/FALSE
TRUE
80. What are the various subevents a mouse double click event
invokes?
Double_clicking the mouse consists of the mouse down,mouse up,mouse click,mouse down and mouse up events.
81 . State any three mouse event System Variables?
SYSTEM.MOUSE_BUTTON_PRESSED
SYSTEM.MOUSE_BUTTON_SHIFT_STATE
SYSTEM.MOUSE_ITEM
SYSTEM.MOUSE_CANVAS
SYSTEM.MOUSE_RECORD
OLE
82. What is an OLE?
Object Linking and Embedding (OLE) provides you with the capability to integrate objectrs from many MS Windows applications into a single compound document. Creating integrated applications enables you to use the features from several MS Windows application.
83. What is the difference between Object Embedding and
Linking in Oracle Forms?
An Ole server applications creates OLE objects that are embedded or linked in OLE containers. Examples of OLE servers are MS Word and MS Excel. OLE containers provide a place to store,display and manipulate objects that are created by OLE server applications.
Example: Oracle Forms is an example of an OLE container
84. What are the different styles of Activation of OLE objects?
In-place Activation
External Activation
Visual Attributes And Property Classes
85. What are Visual attributes?
Visual attributes are the font,color and pattern properties that you set for form and menu objects that appear in your application¡¦s interface.
86. What is a Property Class?
A Property class is a named object that contains a list of properties and their settings. Once you create a property class you can base other objects on it. An object based on a property class inherit the setting of any property in the class that makes sense for that object.
87 . Can a Property class itself be based on a property class?
Yes
88 . What are the Important differences between property
classes and visual attributes?
The important differences betweeen property classes and visual attributes are Named Visual attributes define only font.color and pattern attributes ; property classes can contain these and any other properties.
You can change the appearance of objects at runtime by changing the named visual attribute programmatically; Property class assignment cannot be changed programmatically
When an object is inheriting from both a property class and a named visual attribute, the named visual attribute settings settings take precedence, and any visual attribute properties in the class are ignored.
Forms Built-ins
89. What is a TEXT_IO package?
The Text_IO package allows you to read and write information to a file in the file system.
90. What is an USER_EXIT?
Calls the user exit named in the user_exit_string invokes a 3GL program by name which has been properly linked into your current Oracle Forms executable.
91. What is SYNCHRONIZE?
Synchronizes the terminal screen with the internal state of the form. That is SYNCHRONIZE updates the screen display to reflect the information that Oracle Forms has in its internal representation of the screen.
Triggers
92. What is WHEN-DATABASE-RECORDN Trigger?
Fires when Oracle Forms first marks a record as an insert or an update. That is, the trigger fires as soon as Oracle Forms Determines through validation that the record should be processed by the next post or commit as an insert or update. This generally occurs only when the operator modifies the first item in a record, and after the operator attempts to navigate out of the item.
93. What are Master_Detail Triggers?
ON_CHECK_DELETE_MASTER
ON_CLEAR_DETAILS
ON_POPULATE_DETAILS
System Variables
94. What is the difference between $$DATE$$ and
$$DBDATE$$?
$$$$DBDATE$$ retrieves the current database date
DBDATE$$ retrieves the current operating system date.
95. What is SYSTEM.COORDINATION_OPERATION?
SYSTEM.COORDINATION_OPERATION represents the coordination causing event that occureson the master block in master detail relationship.
Example: System.Cooordination_Operation=
Miscelleneous
96. What are the differences between LOV and List item?
LOV is a Property whereas List item is an item.
A List item can have only one column whereas an LOV can have one or more columns.
97. What are the different display styles of List item?
Poplist
Text list
Combo box.
98 . What is a Poplist?
The poplist style list item appears initially as a single field(similar to a text item field. When The operator selects the list icon, a list of available choices appears.
99 . What is a Text list?
The text list style item appears as a rectangular box which displays a fixed number of values. When the text list contains values that cannot be displayed(due to the display area of the item), a vertical scroll bar appears, allowing the operator to view and select undisplayed values.
100. What is a Combo Box?
The Combo Box style list item combines the features found in list and text items. Unlike the poplist or the text list style list items, the combo box style list item will both display fixed values and accept one operator-entered values.
101. What are Display items?
Display items are similar to text items with the exception that displays items only store and display fetched or assigned values. Display items are generally used asa boilerplate or as conditional text.
102. What is the difference between OPEN_FORM AND
CALL_FORM?
when one form invokes another form by executing OPEN_FORM, the first form remains displayed, and operators can navigate between the forms as desires.
When one form invokes another form by executing CALL_FORM, the called form is modal with respect to the calling form. That is, any windowa that belong to the calling form are disabled and operators cannot navigate to them until they first exit the called form.
103. What is NEW_FORM built-in?
When one form invokes another form by executing New_form, Oracle Forms exists the first form and releases its memeory before loading the new form. Calling NEW_FORM completely replaces the first form with the second. If there are changes pending in the first form, the operator will be prompted to save them before the new form is loaded.
104. what is a Library?
A library is a collection of subprograms, including user- named procedures,functions and packages.
105. What are the advantages of libraries?
Libraries provide a convenient means of storing client-side program units and sharing them among multiple applications.
Once you create a library,you can attach it to any other form,menu or library ,module.
Then, you can call library units from triggers, menu item commands and user-named routines you write in the modules to which modules to which you have attached the library.
When a library attaches another library,program units in the first library can reference program units in the attached library.
Libraries support dynamic loading-that is, a library¡¦s program units are loaded into an application only when needed. This can significantly reduce the runtime memory requirements of an application.
106. What is a STRIP_SOURCE generate option?
Removes the source code from the library file and generates a library file that contains only pcode.
The resulting file can be used for final deployment, but cannot be subsequently edited in the designer.
Example:f45gen module=old_lib.pll userid=scott/tiger
Strip_source=YES output_file=<new_file_name>
107. What are VBX controls?
VBX controls provide a simple method of building and enhancing user interfaces. The controls can be used to obtain user input and display program output. The controls can be used to obtain user input and display program output. VBX controls were originally developed as extensions for the MS Visual Basic environment and include such items as sliders,grids and knobs.
108. What is a Timer?
A timer is an ¡§internal time clock¡¨ that you programatically create to perform an action each time the timer expires.
109. What are the built-ins associated with timers?
FIND_TIMER
CREATE_TIMER
DELETE_TIMER
110. What is the difference between POST-DATABASE-COMMIT
and POST-FORM-COMMIT?
POST-FORM-COMMIT fires once during the Post and Commit Transactions process, after the database commit occurs. The Post-Forms-Commit trigger fires after inserts, updates and deletes have been posted to the database, but before the transaction has been fibalized by issuing the commit. The Post-Database-Commit Trigger fires after Oracle Forms issues the Commit to finalize the transaction.
111. What is the difference between PRE-SELECT and PRE-
QUERY?
Fires during Execute Query and Count Query processing, after Oracle Forms constructs the SELECT statement to be issued, but before the statement is actually issued.
The Pre-Query trigger fires just before Oracle Forms
issues the SELECT statement to the database, after the operator has defined the example record by entering query criteria in Enter Query Mode.
Pre-Query trigger fires before Pre-Select trigger.
112. What is the trigger associated with the TIMER?
WHEN-TIMER-EXPIRED
113. What is the use of the Transactional Triggers?
Using Transactional triggers we can control or modify the default functionality of the Oracle Forms.
ORACLE FORMS 4.5 NOTES
Program units : User-named procedures, functions, or packages, can be defined in forms, menus, or library modules.
Application Partitioning : PL/SQL engine is available on both PL/SQL is the language used for both client-side Oracle Forms applications and server-side database triggers and stored procedures, and there is a PL/SQL engine in both Oracle Forms Runform and the Oracle7 Server. This means that you can take advantage of application partitioning to execute application code on either the client or the server. Application partitioning allows you to optimize performance and resource usage by storing and executing procedures either locally or at the server, whichever makes the most sense for your particular application and configuration.
Navigator Views :
Ownership View : In the ownership view, all form objects are visible, and the display hierarchy corresponds to the Oracle Forms object ownership hierarchy: form--block--item. Items and relations are owned by blocks; blocks are owned by forms; triggers can be owned by forms, blocks, or items; all other form objects (windows, editors, record groups, etc.) are owned by forms.
Module Preference : File, Database, File/Database(Filter dialog)
Default font scaling off : ignores the runtime font, and scales objects according to the size of the default design time font. on :scales objects according to the size of the default runtime font.
Visual View : In the Visual view, only windows, canvas-views, and items are displayed. The Visual view hierarchy corresponds to the hierarchy of objects in a form window: window--canvas-view--item. Items are assigned to canvas-views; canvas-views are assigned to windows. Each window can have multiple canvas-views, and there can be multiple items on a single canvas-view.
Only objects with PL/SQL option displays only code objects
Default Visual attributes : specifies that that the object should be displayed with default color, pattern, and font settings. When Visual Attribute Name is set to Default, the individual attribute settings reflect the current system defaults.
Custom Visual attributes : design time specification
Named visual attributes : specifies that the object should use the attribute settings defined for the named visual attribute
Property class can contain other property classes.
Property class Vs. Named visual attributes :
Named visual attributes define only font, color, and pattern attributes; property classes can contain these and any other properties.
You can change the appearance of objects at runtime by changing the named visual attribute programmatically; property class assignment cannot be changed programmatically.
When an object is inheriting from both a property class and a named visual attribute, the named visual attribute settings take precedence, and any visual attribute properties in the class are ignored.
Variant property : defined separetely in the property window.
Inherit property : inherits from property class.
Copy object option : automatically copies objects owned by the item being copied. gives dialog options for associated objects.
copying a reference object results in referencing only
In referencing when the source object name changes, it has to be updated for all referencing objects in the reference source information property.
Object groups :
An object group is a container for a group of objects. You define an object group when you want to package related objects so you can copy or reference them in another module.
Object groups provide a way to bundle objects into higher-level building blocks that can be used in other parts of an application and in subsequent development projects.
Object groups cannot contain other object groups. Members of object groups should be defined in the same form.
Events : Interface events, Internal processing events
Overview of Trigger Categories
This section provides an overview of commonly used triggers, grouped into the following functional categories:
o block-processing triggers o interface event triggers
o master-detail triggers o message-handling triggers
o navigational triggers o query-time triggers
o transactional triggers o validation triggers
When-Event Triggers : A When-event signals a point at which you can augment Oracle Forms default processing with additional tasks or operations.
On-Event Triggers : An On-event signals a point at which you can replace Oracle Forms default processing.
Pre-Event Triggers : A Pre-event signals a point just prior to the occurrence of either a When-event or an On-event.
Post-Event Triggers : A Post-event signals a point just following the occurrence of either a When-event or an On-event.
Key Triggers : Key triggers have a one-to-one relationship with specific keys. That is, the trigger fires when the operator presses a specific key or key-sequence.
Master-Detail Relationships :
Block Coordination
To maintain the master-detail relationship at runtime, Oracle Forms coordinates the master and detail blocks to ensure that the records displayed in the detail block are associated with the current record in the master block.
Any event that makes a different record in the master block the current record is a coordination-causing event. Deleting a record or pressing [[Up]] or [[Down]] to move to a different record are both examples of coordination-causing events. When such an event occurs, Oracle Forms automatically does the processing necessary to coordinate the master and detail blocks.
There are two phases of block coordination: the clear phase and the population phase. During the clear phase, Oracle Forms navigates internally to the detail block and flushes the obsolete detail records. During the population phase, Oracle Forms issues a SELECT statement to repopulate the detail block with the detail records associated with the new master record. These operations are accomplished through the execution of triggers.
The Copy Value from Item Property
The mechanism that Oracle Forms used to coordinate the population of the detail block with the current record in the master block is the Copy Value from Item property on the foreign key item in the detail block. The Copy Value from Item property specifies the primary key item in the master block whose value gets copied to the foreign key item in the detail block whenever a detail record is created or queried.
Because the value of the primary key item in the master record gets copied to the foreign key item in the detail block, it is automatically incorporated in the WHERE clause of the SELECT statement that Oracle Forms issues to populate the detail block.
When blocks are related through a compound join, the Copy Value from Item property is set on two or more foreign key items in the detail block.
The Relation Object
When you create a relation, Oracle Forms generates the triggers and PL/SQL procedures required to enforce coordination between the master and detail blocks. The actual code that Oracle Forms generates depends on how the properties of the relation are set.
The properties that affect the functionality of a relation include Master Deletes, Coordination, and Prevent Masterless Operation.
Master Deletes Property: The Master Deletes property allows you to specify how the deletion of a record in the master block should affect records in the detail block. It can be set to Non-Isolated, Isolated, or Cascading.
Non-Isolated : The default setting. Prevents the deletion of a master record if associated detail records exist in the database.
Isolated : Allows the master record to be deleted and does not affect the associated detail records in the database.
Cascading: Allows the master record to be deleted and automatically deletes any associated detail records from the base table at commit time. When relations are nested to several levels, only records in the immediate detail block are deleted. That is, deletions do not automatically cascade to multiple levels of a relation chain.
Note: If your database is using the ORACLE7 Server cascading deletes feature, do not use the Cascading deletes option in Oracle Forms.
Coordination Properties :
The Coordination properties Deferred and Auto-Query determine when the population phase of block coordination should occur. Coordination of the detail block with its master can be Immediate, Deferred with Auto-query, or Deferred with No Auto-query.
Immediate (Deferred False, Auto-Query False) The default setting. When a coordination-causing event occurs, the detail records are fetched immediately.
Deferred with Auto-Query (Deferred True, Auto-Query True)When a coordination-causing event occurs, Oracle Forms defers fetching the associated detail records until the operator navigates to the detail block.
Deferred with No Auto-query (Deferred True, Auto-Query False) When a coordination-causing event occurs, Oracle Forms does not automatically fetch the detail records. To fetch the detail records, the operator must navigate to the detail block and explicitly execute a query.
Choosing the Appropriate Coordination
Deferred coordination can more accurately be thought of as "deferred population." That is, when a coordination-causing event occurs in the master block, the population phase of coordination is postponed, but the records in the detail block are cleared immediately. This functionality prevents a detail block from displaying records that are inconsistent with the current record in the master block.
As a general rule, choose immediate coordination (Deferred False, Auto-Query False) when the detail block is visible to the operator, and when it is assumed that the operator will always want to see the detail records associated with the current master record.
Deferred coordination with Auto-query is preferable when the detail block is not immediately visible; for example, when the operator must navigate to the detail block in a different window to be able to view detail records.
Deferred coordination is also useful in situations where the operator may not need to view the detail records at all. In this case, deferring coordination can prevent an unnecessary database query.
Deferred coordination with No Auto-query is useful when you want operators to be able to go into Enter Query mode and specify additional query criteria in the detail block before population occurs. Also, Deferred coordination with No Auto-query allows operators to navigate through detail records without forcing coordination, and its attendant processing, to occur until it is actually required.
Setting the Properties of Foreign Key Items in the Detail Block
When you create a relation, Oracle Forms sets the Copy Value from Item property on the foreign key items in the detail block automatically. The Copy Value from Item property specifies the name of the corresponding primary key item in the format master_block.item_name. At runtime, the value stored in the primary key item in the master block is copied to the foreign key item in the detail block whenever a detail record is created or queried.
When you create the relation in the New Block window, Oracle Forms also alters the properties of the foreign key item(s) in the detail block by doing the following:
o setting the Canvas property to NULL to make the item a NULL-canvas item.
o setting the following properties to False:
o Displayed
o Enabled
o Navigable
o Query Allowed
o Update Allowed
o sequencing items in the Navigator such that the foreign key items are last in the block's navigation sequence
Also, if the relation was created in the New Block window, Oracle Forms does not create a boilerplate text label for the foreign key items.
When you create a relation in the Object Navigator, rather than in the New Block window, you might want to set these same properties yourself.
The purpose of these settings is to hide the foreign key item(s) from the operator, since the same information is likely to be displayed in the primary key item(s) in the detail block. These settings are most appropriate when operators can view both the master and detail blocks at the same time. If operators cannot see the master block when viewing detail records, you may want to undo these settings so that foreign key item(s) are visible to the operator. If you do so, make sure that the item Update Allowed property is set to False, so that operators cannot edit the foreign key value and thus disrupt master-detail coordination.
Deleting a Relation
You can delete a relation by selecting it in the Object Navigator and choosing Navigator->Delete. The following table shows what happens when you delete a relation or an object that is part of a relation:
If you delete... This is the result...
------------------------------------------------------------------------------------------------------
A relation. Oracle Forms deletes all of the master-detail
triggers that were attached to the relation's
master block and clears the Copy Value from
Item property of the foreign key item(s) in the
detail block.
The master or detail block Oracle Forms deletes the relation and all of the
in a relation.master-detail triggers. Oracle Forms does not
delete the master-detail procedures.
A detail block in a Oracle Forms deletes the relation, and removes
master-with-independent- the relevant detail section from the
details relation. On-Clear-Details trigger and, if present, the
On-Populate-Details trigger. Any comments
or code that you added in this section are
removed also.
The foreign key item in a The master-detail block coordination will be
detail block. (Not disrupted. Although the foreign key item in
recommended) the detail block can be hidden by making it a
NULL-canvas item, it cannot be deleted
entirely.
Any master-detail trigger Oracle Forms does not prevent you from
or procedure. (Not deleting a master-detail trigger or procedure.
recommended). Doing so, however, disrupts master-detail
block coordination.
Preventing Masterless Operations in the Detail Block
It is often desirable to prevent operators from peforming masterless operations in a detail block; that is, to prevent them from querying or inserting records in the detail block when there is no current record in the master block.
You can set the Prevent Masterless Operation property to True to prevent operators from performing masterless operations in the detail block of the relation. Setting this property to True has the following effects:
Oracle Forms does not allow records to be inserted in the detail block when there is no master record in the master block. Any attempt to insert a record generates error FRM-41105: Cannot create records without a parent record.
Oracle Forms does not allow querying in the detail block when there is no master record that came from the database in the master block. Any attempt to query generates error FRM-41106: Cannot query records without a parent record.
It is usually appropriate to prevent masterless inserts when operators are likely to encounter an error if they attempt to commit detail records that have been created independently of a master record. Such an error occurs when the detail block derives the value of its foreign-key items from the primary key items in the master record (by way of the Copy Value from Item property).
Similarly, you might want to prevent masterless queries in a detail block because operators cannot perform effective queries from the detail block. Operators can query the existence of specific detail records, but they cannot determine which master records own them. (This assumes that the foreign key item(s) in the detail block are not displayed.)
Preventing Navigation to the Detail Block Setting the Prevent Masterless Operation property to True prevents operators from querying and inserting in a detail block for which there is no corresponding master record, but it does not prevent them from navigating to the detail block and attempting these operations.
In some applications, it may be desirable to disallow any attempt to navigate to a detail block when there is no master record.
The following example shows one way to prevent operators from navigating to a detail block for which there is no master. It is based on the detail block warehouse and the master block region.
When-New-Block-Instance trigger on detail block warehouse:
DECLARE
alert_dummy NUMBER;
BEGIN
/*
** See if there is a master record by checking the status
** of the current record in the master block
*/
IF Get_Record_Property(Get_Block_Property('region',
current_record),'region', STATUS) = 'NEW'
OR :region.region_id IS NULL THEN
/*
** There isn't a master record; display an alert that tells the ** operator to query or enter a region record before moving to
** the warehouse block
*/
alert_dummy := SHOW_ALERT('my_alert');
/*
** Put the input focus in the master block
*/
GO_BLOCK('region');
END IF;
END;
The When-New-Block-Instance trigger fires whenever the operator navigates to the detail block.
The built-in function GET_RECORD_PROPERTY is used to determine the status of the current record in the master block. (The function GET_BLOCK_PROPERTY is nested as the first argument to GET_RECORD_PROPERTY to return the record number of the current record in the region block.)
If the status of the current record is NEW, indicating that the record is not an existing master record, Oracle Forms displays an alert window with the message "Query or enter a master record before moving to the detail block." The trigger then navigates to the master block to allow the operator to do just that.
Creating Complex Master-Detail Relationships
Many applications require complex master-detail relationships that involve more than two blocks. To create such relationships, simply define as many individual relations as needed.
There is no practical limit to the number of relations that can be defined in a form. Further, any block can be the master or detail in more than one relation, and a block that is the master in one relation can be the detail in another.
When you create complex master-detail relationships, Oracle Forms automatically adjusts the existing triggers to manage the relations you define.
This topic describes three of the most common types of complex master-detail relationships:
o master with dependent details o master with independent details
o detail with two masters
Complex Relations and Cascading Deletes
When you set the Master Deletes property of a relation to Cascading, be aware that deletes are enforced only for the immediate detail block in the relation. Thus, in a complex master-detail relationship involving relations between blocks A and B (A_B), and B and C (B_C), if relation A_B is cascading, the detail records in Block C are not automatically deleted unless Relation B_C is also cascading.
Master with Dependent Details
A master with dependent details relationship includes a master block and n levels of detail blocks, such that the first detail block is itself a master for its own detail block.
To create a master with dependent details relationship, define the individual relations A_B and B_C separately. The relations can be created in any order.
When you create this type of relationship, consider the effect of the Master Deletes and Coordination properties on the detail blocks. For example, if one relation in a chain of related blocks is set to deferred coordination, all subsequent blocks will also be deferred. Thus, when relation A_B is deferred and relation B_C is immediate, Oracle Forms does not coordinate Block C with Block B until Block B is coordinated with Block A.
Master with Independent Details
A master with independent details relationship involves two or more detail blocks, each of which has the same master block. This structure is useful when you want to display more than one set of detail records for a single master record. A coordination-causing event in the master block results in both detail blocks being populated with the appropriate detail records.
In the sample application, the master block region could be displayed along with the detail blocks warehouse and customer. The operator could then see all of the warehouses and customers within the currently selected region.
To create this type of relationship, define the individual relations A_B and A_C separately. The relations can be created in any order.
Detail with Two Masters
A detail with two masters relationship involves a single detail block that has two master blocks. Oracle Forms displays the appropriate detail records for whichever master block is the current block in the form. For example, in the sample application referred to earlier, the ord block could be a detail block having two master blocks, customer and emp. The operator could then see all of the orders for a particular customer, or for a particular sales representative (employee).
Usually, when you create a detail with two masters relationship, you will be joining on different foreign key items in the detail block. In such cases, the Copy Value from Item property is set for each foreign key item in the detail block to point to the primary key item in the appropriate master block. To create this type of relationship, you need only define the two relations, and Oracle Forms will automatically support coordination.
In other cases, however, you might want to create a master with two details with each relationship joining on the same foreign key item in the detail block. However, because the Copy Value from Item property can only point to one master block item, you will need to write additional code to coordinate querying and updating for the second relation if you are joining on the same item in the detail block.
Depending on the desired functionality, this might include writing a Pre-Query trigger for the detail block to ensure that the correct primary key item value is copied to the foreign key item in the detail block. For example,
Copy(name_in(:System.Master_Block||'.primary_key_item'),
'detail_block.item');
You might also want to create a When-New-Block-Instance trigger that checks the coordination status of the detail block whenever the operator navigates to a different master block, and, if necessary, populates the detail block. For more information on triggers and built-ins available for customizing master-detail functionality, refer to "Modifying the Default Master-Detail Functionality."
About Master-Detail Triggers and Procedures
When you create a relation, Oracle Forms generates different triggers depending on how the Master Deletes and Coordination properties are set. The following table shows how the Master Deletes property determines which triggers Oracle Forms creates. When you change the setting of the Master Deletes property for an existing relation, Oracle Forms adds or removes triggers as needed. The actual code in these triggers depends on how the Coordination properties are set, and on whether the relation is part of a complex relation chain.
Master Deletes Property Resulting Triggers
-----------------------------------------------------------------------------------------------------
Non-Isolated (the default) On-Check-Delete-Master
On-Clear-Details
On-Populate-Details
Cascading On-Clear-Details
On-Populate-Details
Pre-Delete
Isolated On-Clear-Details
On-Populate-Details
Master-Detail Triggers
This section describes the triggers that Oracle Forms creates when you define a master-detail relationship. The example trigger text shown with each trigger description shows the basic structure of the trigger. The actual trigger text that you will see in your own forms will be application-specific, and may look somewhat different.
Oracle Forms also creates user-named procedures that are called by master-detail triggers.
Oracle Forms generates comments in the default trigger and procedure code. Comments are denoted by the standard PL/SQL double-hyphen ('- -').
On-Clear-Details Trigger The On-Clear-Details trigger is required for all master-detail relations. It fires during the clear phase of coordination, and clears all of the detail records in the detail block. This trigger calls the CLEAR_ALL_MASTER_DETAILS procedure, as shown in the following example trigger text:
-- Begin default relation program section
--
Clear_All_Master_Details;
--
-- End default relation program section
--
On-Check-Delete-Master Trigger Oracle Forms creates the On-Check-Delete-Master trigger when the Master Deletes property is set to Non-Isolated. It fires when there is an attempt to delete a master record. The trigger queries the database to see if detail records exist for the master record. If no details exist, the trigger deletes the master record. If detail records are found, the trigger displays the message "Cannot delete master record when matching detail records exist." as shown in the following example trigger text:
-- Begin default relation declare section
--
Declare
Dummy_Define char(1);
--
-- Begin B detail declare section
--
cursor B_cur is
select null from MASDET
where PARENT = :A.ID;
--
-- End B detail declare section
--
--
-- End default relation declare section
--
--
-- Begin default relation program section
--
Begin
--
-- Begin B detail program section
--
Open B_cur;
Fetch B_cur into Dummy_Define;
if ( B_cur%found ) then
Message('Cannot delete master record when matching
detail records exist.');
Close B_cur;
raise Form_Trigger_Failure;
end if;
Close B_cur;
--
-- End B detail program section
--
End;
--
-- End default relation program section
On-Populate-Details Trigger Oracle Forms creates the On-Populate-Details trigger for every master-detail relation. It fires during the population phase of block coordination.The trigger first checks the status of the master record and the value of its primary key field, then navigates to the detail block to issue the appropriate query. This trigger calls the QUERY_MASTER_DETAILS procedure, as shown in the following example trigger text:
-- Begin default relation declare section
--
Declare
recstat char(20) := :system.record_status;
start_item char(61) := :system.cursor_item;
relation_id relation;
--
-- End default relation declare section
--
-- Begin default relation program section
--
Begin
if ( recstat = 'NEW' or recstat = 'INSERT' ) then
return;
end if;
--
-- Begin B detail program section
--
if ((:A.ID is not null)) then
relation_id := find_relation('A.AB');
Query_Master_Details(relation_id, 'B');
end if;
--
-- End B detail program section
----
End;
Pre-Delete Trigger Oracle Forms creates the Pre-Delete trigger when the Master Deletes property is set to Cascading. It deletes the records in the detail block's base table that correspond to the master record that is being deleted.
-- Begin default relation program section
--
BEGIN
--
-- Begin detail_block detail program section
--
DELETE FROM detail_block_base_table
WHERE foreign_key_column = :master_block.primary_key_item;
--
-- End detail_block detail program section
--
END;
--
-- End default relation program section
Master-Detail Procedures
This section shows the text of the master-detail procedures that Oracle Forms creates automatically when you define a relation. These procedures are called from the master-detail triggers or from other procedures.
CLEAR_ALL_MASTER_DETAILS Procedure This procedure is called by the On-Clear-Details trigger. It navigates to the detail block and clears the detail records.
PROCEDURE Clear_All_Master_Details IS
mastblk CHAR(30); /* Initial Master Block Causing Coord */
coordop CHAR(30); /* Operation Causing the Coord */
trigblk CHAR(30); /* Cur Block On-Clear-Details Fires On*/
startitm CHAR(61); /* Item in which cursor started */
frmstat CHAR(15); /* Form Status */
curblk CHAR(30); /* Current Block */
currel CHAR(30); /* Current Relation */
curdtl CHAR(30); /* Current Detail Block */
FUNCTION First_Changed_Block_Below( Master CHAR ) RETURN CHAR
IS
curblk CHAR(30); /* Current Block */
currel CHAR(30); /* Current Relation */
retblk CHAR(30); /* Return Block */
BEGIN
/*
** Init Local Vars
*/
curblk := Master;
currel :=Get_Block_Property(curblk,FIRST_MASTER_RELATION);
/*
** While there exists another relation for this block
*/
WHILE currel IS NOT NULL LOOP
/*
** Get the name of the detail block
*/
curblk := Get_Relation_Property(currel,DETAIL_NAME);
/*
** If this block has changes, return its name
*/
IF Get_Block_Property(curblk,STATUS) IN
('CHANGED','INSERT') THEN
RETURN curblk;
/*
** Otherwise, recursively look for changed blocks below
*/
ELSE
retblk := First_Changed_Block_Below(curblk);
/*
** If some block below is changed, return its name
*/
IF retblk IS NOT NULL THEN
RETURN retblk;
/*
** Otherwise, Consider the next relation
*/
ELSE
currel := Get_Relation_Property (currel,
NEXT_MASTER_RELATION);
END IF;
END IF;
END LOOP;
/*
** If we get here, no changed blocks were found
*/
RETURN NULL;
END First_Changed_Block_Below;
BEGIN
/*
** Init Local Vars
*/
mastblk := :System.Master_Block;
coordop := :System.Coordination_Operation;
trigblk := :System.Trigger_Block;
startitm := :System.Trigger_Item;
frmstat := :System.Form_Status;
/*
** If the coord op is anything but CLEAR_RECORD, then
** continue checking.
*/
IF coordop <> 'CLEAR_RECORD' THEN
/*
** If we're processing the driving master block...
*/
IF mastblk = trigblk THEN
/*
** If something in the form is changed, find the
** first changed block below the master
*/
IF frmstat = 'CHANGED' THEN
curblk := First_Changed_Block_Below(mastblk);
/*
** If we find a changed block below, go there
** and Ask to commit the changes.
*/
IF curblk IS NOT NULL THEN
Go_Block(curblk);
Check_Package_Failure;
Clear_Block(ASK_COMMIT);
/*
** If user cancels commit dialog, raise error
*/
IF NOT( :System.Form_Status = 'QUERY' /* Yes */ OR
:System.Block_Status = 'NEW' /* No */ ) THEN
RAISE Form_Trigger_Failure;
END IF;
END IF;
END IF;
END IF;
END IF;
/*
** Clear all the detail blocks for this master without
** any further asking to commit.
*/
currel := Get_Block_Property(trigblk,FIRST_MASTER_RELATION);
WHILE currel IS NOT NULL LOOP
curdtl := Get_Relation_Property(currel,DETAIL_NAME);
IF ( Get_Block_Property(curdtl, STATUS) <> 'NEW' ) THEN
Go_Block(curdtl);
Check_Package_Failure;
Clear_Block(NO_VALIDATE);
IF ( :System.Block_Status <> 'NEW' ) THEN
RAISE Form_Trigger_Failure;
END IF;
END IF;
currel := Get_Relation_Property(currel,NEXT_MASTER_RELATION);
END LOOP;
/*
** Put cursor back where it started
*/
IF ( :System.Cursor_Item <> startitm ) THEN
Go_Item(startitm);
END IF;
EXCEPTION
WHEN Form_Trigger_Failure THEN
IF :System.Cursor_Item <> startitm THEN
Go_Item(startitm);
END IF;
RAISE;
END Clear_All_Master_Details;
QUERY_MASTER_DETAILS Procedure This procedure is called from the On-Populate-Details trigger. It navigates to the detail block and then executes a query to fetch the appropriate detail records.
PROCEDURE Query_Master_Details(rel_id Relation, detail CHAR) IS
oldmsg CHAR(2); /* Old Message Level Setting */
reldef CHAR(5); /* Relation Deferred Setting */
BEGIN
/*
** Initialize Local Variable(s)
*/
reldef := Get_Relation_Property(rel_id,
DEFERRED_COORDINATION);
oldmsg := :System.Message_Level;
/*
** If NOT Deferred, Goto detail & execute the query.
*/
IF reldef = 'FALSE' THEN
Go_Block(detail);
Check_Package_Failure;
:System.Message_Level := '5';
Execute_Query;
:System.Message_Level := oldmsg;
/*
** If Deferred, Mark the detail block as un-coordinated
*/
ELSE
Set_Block_Property(detail, coordination_status,
NON_COORDINATED);
END IF;
EXCEPTION
WHEN Form_Trigger_Failure THEN
:System.Message_Level := oldmsg;
RAISE;
END Query_Master_Details;
CHECK_PACKAGE_FAILURE Procedure This procedure is called by the CLEAR_ALL_MASTER_DETAILS and QUERY_MASTER_DETAILS procedures. It checks to see if the previous statement executed successfully by looking at the status of the built-in Oracle Forms error variable FORM_SUCCESS.
PROCEDURE Check_Package_Failure IS
BEGIN
IF (NOT Form_Success) THEN
RAISE Form_Trigger_Failure;
END IF;
END;
Triggers for Complex Master-Detail Relations
When you create a complex master-detail relationship, Oracle Forms adds or edits the existing master-detail triggers to support the relationship you have defined. The following examples illustrate how Oracle Forms adds or edits triggers as required.
Example 1: Master with Independent Details Consider a single relation A_B, with Master Deletes set to Non-Isolated and Coordination set to Immediate (default settings). Oracle Forms creates the following triggers on the master block to manage the relation:
o On-Clear-Details o On-Check-Delete-Master
o On-Populate-Details
If you then create a second relation A_C (having the same master block but a different detail block), you have created a master-with-independent-details relationship; that is, one master block with two detail blocks.
To manage this relationship, Oracle Forms does not create any additional triggers. Instead, Oracle Forms adds a section to each existing trigger to facilitate clearing and populating the second detail block. The generated comments in these triggers delimit the sections that manage each detail block. For example, the comments in the On-Populate-Details trigger clearly show where each detail block section begins and ends:
-- Begin default relation program section
BEGIN
--
-- Begin first_detail_block program section
--
/* trigger text to clear the first detail block*/
--
-- End first_detail_block program section
--
--
-- Begin second_detail_block program section
--
/* trigger text to clear the second detail block*/
--
-- End second_detail_block program section
--
/* final trigger text */
END;
-- End default relation program section
--
Example 2: Master with Dependent Details In this example, the simple relation A_B is extended by adding a second relation B_C to create a master with dependent details relationship.
To manage the second relation B_C, Oracle Forms removes the form-level On-Clear-Details trigger, and creates two additional triggers that enforce coordination with the new detail block. The additional triggers are attached to Block B, the master for the second relation (B_C).
Modifying the Default Relation Triggers
You may at some point want to add your own comments and code to the default master-detail triggers that Oracle Forms creates. You can edit a default trigger as you would any trigger that you had created yourself.
Remember, however, that if you later change the properties of the relation, Oracle Forms may need to delete or edit the default triggers. For example, changing a relation's Master Deletes property from Cascading to Isolated causes Oracle Forms to remove the now unnecessary Pre-Delete trigger.
Consider the following points when you edit master-detail triggers:
o Do not alter or delete the comments that Oracle Forms generates. These comments tell Oracle Forms where to insert or delete trigger text when changes are necessary.
o If you add code to a trigger, insert it before the "Begin default relation program section" comment or after the "End default relation program section" comment.
o Oracle Forms does not delete a master-detail trigger that you have modified, provided that you place your code outside the default relation program section. (Oracle Forms removes the relation program section, but does not delete the trigger.)
Modifying the Default Master-Detail Functionality
In special situations, you may want to modify or extend the default master-detail functionality that Oracle Forms provides. For example, if your application runs against non-ORACLE data sources or includes long relation chains that require non-standard functionality, you might want to implement your own block coordination mechanism.
Oracle Forms provides a number of triggers and built-in subprograms that are useful for such tasks, some of which are listed here. For complete information on these triggers and routines, refer to the Oracle Forms Reference Manual, Vol. 1.
Triggers:
o On-Clear-Details o On-Populate-Details
o On-Check-Delete-Master o When-New-Record-Instance
o When-New-Block-Instance
Built-in subprograms:
o GET_BLOCK_PROPERTY o SET_BLOCK_PROPERTY
o GET_FORM_PROPERTY o GET_RELATION_PROPERTY
o SET_RELATION_PROPERTY
For example, you can use these built-in subprograms as follows:
o Use GET_FORM_PROPERTY to get the name of the first and last block in the form (FIRST_BLOCK, LAST_BLOCK).
o Use GET_BLOCK_PROPERTY to find out a block's current COORDINATION_STATUS (either COORDINATED or NON_COORDINATED) and a block's FIRST_RELATION, that is, the name of the first relation in which the block is a master.
o Use SET_BLOCK_PROPERTY to set block properties dynamically.
o Use GET_RELATION_PROPERTY to get the current property settings for a relation (MASTER_DELETES, DEFERRED_COORDINATION, and AUTOQUERY), the names of the master and detail blocks (MASTER_NAME, DETAIL_NAME), and the name of the next relation in the form (NEXT_MASTER_RELATION, NEXT_DETAIL_RELATION). For example, to assign the name of the master block in a relation to a local variable you might write the following:
DECLARE
master_block VARCHAR2;
BEGIN
master_block := Get_Relation_Property('my_relation',
MASTER_BLOCK);
END;
o Use SET_RELATION_PROPERTY to set the properties of a relation dynamically. For example, to set the Master Deletes property you could call the following procedure:
Set_Relation_Property('my_relation', MASTER_DELETES,
DEFERRED_COORDINATION);
Canvas-Views
Canvas-views are the background objects on which you place the interface items (text items, check boxes, radio groups, etc.) and boilerplate objects (boxes, lines, images, etc.) that operators interact with as they run your form. Each canvas-view is displayed in a window.
Content Canvas-Views Most canvas-views are content canvas-views. A content canvas-view is the "base" view that occupies the entire content pane of the window in which it is displayed. You must define at least one content canvas-view for each window you create. More than one content canvas-view can be assigned to the same window at design time, but at runtime, only one of them at a time is displayed in the window.
Stacked Canvas-Views A stacked canvas-view is displayed in a window on top of, or "stacked" on the content canvas-view assigned to that same window. Stacked canvas-views obscure some part of the underlying content canvas-view, and are often shown and hidden programmatically. More than one stacked canvas-view can be displayed in a window at the same time.
Horizontal/Vertical Toolbar Canvas-Views Toolbar canvas-views are used to create toolbars for individual windows. Horizontal toolbars are displayed at the top of a window, just under its menu bar. Vertical toolbars are displayed along the left side of a window.
Windows
MDI applications display a default parent window, called the application window. All other windows in the application are either document windows or dialog windows.
Document windows are always displayed within the MDI application window frame. If the operator resizes the application window so that it is smaller than a document window, the document window is clipped. Operators can maximize a document window so that it occupies the entire content area of the application window.
Dialog windows are free-floating, and the operator can move them outside the application window if they are defined as Movable. If the operator resizes the application window to make it smaller than a dialog window, the dialog window is not clipped.
A window can be either modeless or modal.
Modeless windows can remain displayed until they are dismissed by the operator or hidden programmatically. You can set the Remove on Exit property for a modeless window to specify whether it should remain displayed when the operator navigates to another window.
Modal windows are usually used as dialogs, are often displayed with a platform-specific border unique to modal windows. On some platforms, modal windows are "always-on-top" windows that cannot be layered behind modeless windows.
In addition to platform-specific restrictions, modal windows have the following characteristics:
The Remove on Exit property does not apply to modal windows. By default, Oracle Forms prevents operators from navigating out of modal windows with the mouse, but does allow them to navigate to another window with keyboard commands. When such navigation occurs, Oracle Forms always closes the modal window, unless the target window is itself a modal window.
Modal windows cannot have scroll bars, and setting the Scroll Bar properties for a modal window has no effect.
Show_lov : the lov need not be attached to the text item.
List_values : the lov should be attached to the text item.
lovs are based on record groups.
Changing a column in the record group does not update lov columns automatically
Record Groups :
The following built-in subprograms are available for creating and manipulating record groups programmatically:
Creating and deleting groups:
o CREATE_GROUP (function) o CREATE_GROUP_FROM_QUERY (function)
o DELETE_GROUP (procedure)
Modifying a group's structure:
o ADD_GROUP_COLUMN (function) o ADD_GROUP_ROW (procedure)
o DELETE_GROUP_ROW (procedure)
Populating groups:
o POPULATE_GROUP (function)
o POPULATE_GROUP_WITH_QUERY (function)
o SET_GROUP_CHAR_CELL (procedure)
o SET_GROUP_DATE_CELL (procedure)
o SET_GROUP_NUMBER_CELL (procedure)
Getting cell values:
o GET_GROUP_CHAR_CELL (function)
o GET_GROUP_DATE_CELL (function)
o GET_GROUP_NUMBER_CELL (function)
Processing rows:
o GET_GROUP_ROW_COUNT (function)
o GET_GROUP_SELECTION_COUNT (function)
o GET_GROUP_SELECTION (function)
o RESET_GROUP_SELECTION (procedure)
o SET_GROUP_SELECTION (procedure)
o UNSET_GROUP_SELECTION (procedure)
Object ID functions:
o FIND_GROUP (function)
o FIND_COLUMN (function)
Populate Group with query : can be used to modify record group at run time but columns cannot be altered ( created during design time).
To populate a list item during run time using record group, the record group must contain two columns of char type
Oracle Forms Datatypes
The following table shows the FIND_ function and return type for each object:
Object Function Return Type
Alert FIND_ALERT ALERT
Block FIND_BLOCK BLOCK
Canvas FIND_CANVAS CANVAS
Record Group Column FIND_COLUMN GROUPCOLUMN
Editor FIND_EDITOR EDITOR
Form FIND_FORM FORMMODULE
Record Group FIND_GROUP RECORDGROUP
Item FIND_ITEM ITEM
List of Values FIND_LOV LOV
Menu Item FIND_MENU_ITEM MENUITEM
Parameter List GET_PARAMETER_LIST PARAMLIST
Relation FIND_RELATION RELATION
Timer FIND_TIMER TIMER
View FIND_VIEW VIEWPORT
Using object id improves performance, makes code generic and easier to maintain.
Each time you reference an object by name in a PL/SQL statement, Oracle Forms does the necessary processing to look up the object's ID internally.
Default_value built in procedure assigns the value to the indicated variable only if it is null.
Consider the following factors when deciding whether to use a global or NULL-canvas item as a variable:
o Items can be defined as CHAR, NUMBER, or DATE data types; global variables store only character strings, and using conversion functions like TO_DATE and TO_NUMBER requires additional processing.
o Items can be dimensioned by setting their Maximum Length property; global variables are always 255 bytes.
o Global variables are visible across multiple modules during a runtime session; NULL-canvas items are not.
o The CLEAR_FORM operation sets the value of a NULL-canvas item in the current form to NULL; the value of a global variable is not affected by CLEAR_FORM.
o Both items and global variables can be referenced in the default WHERE clause for a base table block and record group SQL statements.
Subprograms and functions :
Defined in a form module can be called only in that module
Defined in a library can be called from anywhere.
PL/SQL Packages:
A package is a PL/SQL construct that groups logically related types, objects, procedures, and functions. Packages usually have two parts, a specification and a body, although sometimes the body is unnecessary.
The first time a package is called (by any user on the instance) the entire package is loaded into the Oracle7 SGA to make subsequent invocation of any procedures or functions it contains very fast.
LIBRARIES
A library is a collection of subprograms, including user-named procedures, functions, and packages. Libraries provide a convenient means of storing client-side program units and sharing them among multiple applications. A library can be attached to any form, menu, or library module. Then, you can call library program units from triggers, menu item commands, and user-named routines you write in the modules to which you have attached the library. The same library can be attached to multiple forms and menus. Conversely, a single form or menu can have more than one attached library.
Libraries can also be attached to other libraries. When a library attaches another library, program units in the first library can reference program units in the attached library.
Libraries support dynamic loading --that is, a library's program units are loaded into an application only when needed. This can significantly reduce the runtime memory requirements of an application.
File formats : .pll - source and compiled (pcode) source can be removed using STRIP_SOURCE. .pld - only source
libraries cannot refer - form variables, system variables, global variables, form parameters
Instead use name_in, copy for referencing
Unlike PL/SQL menu items, a user-defined trigger defined in a form module can refer directly to the values of form items. If you want to write a user-named routine or anonymous block that uses direct references, you can place it in a user-named trigger and then call that trigger from a PL/SQLmenu item command with the EXECUTE_TRIGGER built-in
Menus :
Background Menu : only one per menu module. it is assigned the name BGM.
Features :
* There is a logical key associated with the first 10 menu items on the background menu. Operators can press a background menu key to execute the command assigned to a background menu item, without having to select the item on the BGM menu.
* At any time, operators who have been granted background menu privileges can display the items on the background menu in a separate "show-keys" window by pressing [[Show BGM]]. Similarly, the background menu can be displayed programmatically by executing the SHOW_BACKGROUND_MENU routine.
PECS : Performance event collection services
FORMS 4.5 ADVANCED TECHNIQUES MANUAL
Exceptions :
When a built - in failes, no exception is raised, subsequent statements are executed. So the outcome of the built-ins is to be tested;
User named triggers :
When an unhandled exception is raised in a user-named trigger, the user-named trigger fails, but the exception does not propagate to the calling trigger. Rather, Oracle Forms treats the failure as an error in the built-in procedure EXECUTE_TRIGGER, and sets the return values of the built-in error functions accordingly. Thus, the outcome of a user-named trigger can be trapped in the same way as a call to any other built-in subprogram; that is, by evaluating the built-in error functions:
Error Handling for Stored Procedures
There are three primary methods for trapping ORACLE errors that are returned from the kernel during the processing of your PL/SQL code:
o checking DBMS_ERROR_TEXT and DBMS_ERROR_CODE built-in subprograms within a form-level ON-ERROR trigger
o creating appropriate user-defined exceptions
o evaluating the SQLCODE and SQLERRM functions in a WHEN OTHERS exception handler
User defined exceptions :
exception_init : associate an oracle error number with an exception name of our choice.
Multiple form applications
There are three ways that one form can programmatically invoke another form:
o Execute the OPEN_FORM procedure to open an independent form.
o Execute the NEW_FORM procedure to replace the current form with a different form.
o Execute the CALL_FORM procedure to call a modal form.
When one form invokes another form by executing OPEN_FORM, the first form remains displayed, and operators can navigate between the forms as desired. An opened form can share the same database session as the form from which it was invoked, or it can create a separate session of its own. For most GUI applications, using OPEN_FORM is the preferred way to implement multiple-form functionality.
When one form invokes another form by executing NEW_FORM, Oracle Forms exits the first form and releases its memory before loading the new form. Calling NEW_FORM completely replaces the first form with the second. If there are changes pending in the first form, the operator will be prompted to save them before the new form is loaded.
When one form invokes another form by executing CALL_FORM, the called form is modal with respect to the calling form. That is, any windows that belong to the calling form are disabled, and operators cannot navigate to them until they first exit the called form.
Multiple-Form Applications and the Root Window
Only one root window can be displayed even in multiple form applns. So root windows are to be avoided when more than one form is to be displayed at the same time.
If form a has a root window defined and invokes form b which also has root window, form b is displayed on the root window of a thus hiding form a.
Opening forms in different database sessions :
To open a form without creating a new session:
Open_Form('stocks'); -- default; NO_SESSION is implicit
Open_Form('stocks',ACTIVATE,NO_SESSION) -- explicit; for clarity
To open a form in its own, independent session, call OPEN_FORM with the SESSION parameter, as shown here:
Open_Form('stocks',ACTIVATE,SESSION);
When COMMIT is initiated, processing is done for those forms that share the same session.
Opening multiple instances of the same form :
To navigate use form id.
Post Vs Commit :
Posting consists of writing updates, deletions, and insertions in the form to the database, but not committing these transactions to the database. Oracle Forms does all of the default validation and commit processing, but does not issue the COMMIT statement to finalize these transactions. If posted the status of the records need not be maintained in the form.
Commit finalizes these transactions
Post only mode :
When a calling form has pending updates or deletes that have not been explicitly posted, Oracle Forms runs the called form in post-only mode.
Commiting from child form :
update records in form A, post , call form B, make changes and commit.
Commiting from parent form :
update records in form A, call form B, post return to A in no-rollback mode and commit.
Calling Other Products from Oracle Forms
You can invoke other products from Oracle Forms with the RUN_PRODUCT built-in procedure. The syntax for RUN_PRODUCT is shown here:
RUN_PRODUCT(product, document, commmode, execmode, location,
list, display);
For example, to invoke Oracle Reports, you could make the following call:
Run_Product(REPORTS,'stats',ASYNCHRONOUS,BATCH,FILESYSTEM);
By default, when you invoke Oracle Reports or Oracle Graphics with RUN_PRODUCT, the called product logs on to ORACLE using the current form operator's USERID.
Oracle Forms uses the parameters you pass to RUN_PRODUCT to construct a valid command line invocation of the called product. RUN_PRODUCT takes the following parameters:
Product A numeric constant that specifies the Oracle tool to be invoked: FORMS, REPORTS, GRAPHICS, or BOOK.
Document Specifies the document or module to be opened by the called product.
Commmode Specifies the communication mode to be used when running the called product. Valid numeric constants for this parameter are SYNCHRONOUS and ASYNCHRONOUS.
o SYNCHRONOUS specifies that control returns to Oracle Forms only after the called product has been exited. The operator cannot work in the form while the called product is running. Synchronous is required when passing a record group to a called product as a DATA_PARAMETER; for example, when invoking Oracle Graphics to return an Oracle Graphics display that will appear in a form chart item.
o ASYNCHRONOUS specifies that control returns to the calling application immediately, even if the called application has not completed its display. Do not use ASYNCHRONOUS when passing a record group to a called product as a DATA_PARAMETER; for example, when invoking Oracle Graphics to return an Oracle Graphics display that will appear in a form chart item.
Execmode Specifies the execution mode to be used when running the called product, either BATCH or RUNTIME. When you run Oracle Reports and Oracle Graphics, execmode can be either BATCH or RUNTIME. When you run Oracle Forms, always set execmode to RUNTIME.
Location Specifies the location of the document or module you want the called product to execute, either the file system or the database.
List Specifies the name or ID of a parameter list to be passed to the called product.
Display Specifies the name of the Oracle Forms chart item that will contain the display generated by Oracle Graphics.
Chart item : Does not store database values. contains objects generated by oracle graphics
OLE :Object Linking and Embedding (OLE) provides you with the capability to integrate objects from many MS Windows applications into a single compound document. In Oracle Forms, embedded objects become part of the form module, and linked objects are references from a form module to a linked source file. Embedded objects are activated by In-place/ External activations. Linked objects - External activation
An OLE server application creates objects that are embedded or linked in OLE containers; OLE containers store and display OLE objects. Oracle Forms is an OLE container application, and MS Word is an example of an OLE server application.OLE server applications can create many object classes. During the installation of an OLE server application, the object classes that an OLE server can create are installed in a registration database. When you install MS Windows applications that support OLE, a registration database is created on your computer, if it does not already exist. The registration database contains the object classes that are valid for embedding and linking into a form module. For instance, MS Word classes include MS Word 6.0 Document, MS Word 6.0 Picture, and MS WordArt 2.0.
OLE objects are documents created from OLE server applications such as MS Word. Another example of an OLE object is a spreadsheet created in MS Excel. OLE objects are linked or embedded into compound documents created by OLE container applications such as Oracle Forms.
Embedded Objects
An embedded object, such as a spreadsheet or chart, is created by an MS Windows OLE server application and is embedded in an Oracle Forms form module. An embedded object is stored as part of a form module or as an item in the database.
You can modify the content of an embedded object within Oracle Forms if the OLE server application that created the OLE object is accessible by your computer. Editing an embedded object is performed with in-place activation or external activation.
An example of object embedding is to insert an MS Excel spreadsheet in an OLE container of a form module. The MS Excel spreadsheet is stored as part of the form module or as an item in the database; there is no separate source file containing the Excel spreadsheet.
Linked Objects
A linked object, such as a word processor document, is created by an MS Windows OLE server application. A linked object is stored in a separate source file created from an OLE server application. An image representation of the linked object and information about the location of the linked object's source file is stored in a form module or as item in the database. The content of the linked object is not stored as part of a form module or in the database; it is retained in a separate file known as the linked source file.
An example of object linking is to link an MS Word document in a form module. An image of the MS Word document appears in the OLE container of the form module and the location of the MS Word file is stored as part of the form module or as an item in the database.
In-Place Activation : When container surrounds the object ( oracle forms surrounding the spreadsheet) Some of the forms menu is replaced by the objects menu. to deactivate click outside the window
External Activation : is started in a separate window. does not replace forms menu/toolbar to deactivate explicit quit is required.
An OLE container in Oracle Forms is a type of custom item. A custom item in Oracle Forms can be an OLE Container, VBX Control, or User Area. In an OLE container, you can link or embed OLE objects. OLE objects can be used as base table items or contol items.
VBX Controls : VBX controls provide a simple method of building and enhancing user interfaces. The controls can be used to obtain user input and display program output.
VBX Controls in Oracle Forms :
A VBX control in Oracle Forms is a type of custom item. A custom item in Oracle Forms can be an OLE Container, VBX Control, or User Area. Like other Oracle Forms item types, VBX controls serve as a way to represent and manipulate data that displays on a form. VBX controls can be used as base table items or control items.
VBX Control as an Oracle Forms Item :
You can interchange a VBX control with other Oracle Forms items without affecting your intended use for the item. A text item in Oracle Forms displays data from the database on a form. A VBX control can accomplish the same task. For example, a text item displaying the number 10 can be depicted by a VBX control that is a knob. Both items also reflect changes in the data from the database. For instance, when the number 10 changes to the number 5, the number 5 appears in the text item on the form and the knob control redirects its position to represent the number 5.
PL/SQL Interface to Foreign Functions :
Foreign functions can be accessed through a user exit interface or through a PL/SQL interface. In most instances, creating user exit interface requires relinking Oracle Forms Runtime. Creating a PL/SQL interface to foreign functions requires the use of the ORA_FFI built-in package (Oracle Foreign Function Interface). The ORA_FFI package provides a public interface for calling foreign functions from PL/SQL. There are many benefits for accessing foreign functions through a PL/SQL interface:
o Additional code in the foreign function source code is not required.
o Tools for compiling and linking the foreign function are not necessary.
o Conflicts with shared libraries such as dynamic link libraries (DLLs)are reduced or eliminated.
o Relinking Oracle Forms Runform is not required.
Using a PL/SQL interface provides a much looser bind than that of a user exit interface, because accessing foreign functions through a user exit interface depends on a single dynamic link library and usually requires the relinking of Oracle Forms Runform.
ORA_FFI Package :
To access a foreign function through a PL/SQL interface, you need to know the foreign function's prototype and function's location. Relinking Oracle Forms and creating dynamic link libraries are unnecessary when using a PL/SQL interface to access foreign functions.
Types of Foreign Functions :
o Oracle Precompiler foreign functions
o OCI (ORACLE Call Interface) foreign functions
o non-ORACLE foreign functions
You can also write foreign functions that combine both the ORACLE Precompiler interface and the OCI.
Oracle Precompiler foreign functions :
With embedded SQL commands, an Oracle Precompiler foreign function can access Oracle databases as well as Oracle Forms variables and items. Although it is possible to access Oracle Forms variables and items, you cannot call Oracle Forms built-in subprograms from a foreign function. You can access Oracle Forms variables and items because you can use a set of Oracle precompiler statements that provide this capability.
OCI (ORACLE Call Interface) Foreign Functions :
An OCI foreign function incorporates the Oracle Call Interface. This interface allows you to write a subprogram that contains calls to Oracle databases. A foreign function that incorporates only the OCI (and not the Oracle Precompiler interface) cannot access Oracle Forms variables and items.
Non-Oracle Foreign Functions :
A non-Oracle foreign function does not incorporate either the Oracle Precompiler interface or the OCI. For example, a non-Oracle foreign function might be written entirely in the C language. A non-Oracle foreign function cannot access Oracle databases or Oracle Forms variables and items.
1. What built-in can you use to open a second form but keep the first form in control?
A*. OPEN_FORM
B . SYSTEM.MOUSE_FORM
C . SYSTEM.CURRENT_FORM
D . CALL_FORM
E . FIND_FORM
Explanation:
OPEN_FORM
The OPEN_FORM built-in includes a NO_ACTIVATE option stipulating that the form being opened should not receive control.
2. Which system variable can tell you the record on which the user has placed focus?
A . CURSOR_ITEM
B . CURRENT_RECORD
C*. CURSOR_RECORD
D . CURRENT_ITEM
Explanation:
CURSOR_RECORD
This is a record-level requirement, so the ITEM variables will not help you. There is no CURRENT_RECORD system variable.
3. You are modifying a Customer form so that it has the ability to place the contents of the customer's ZIP code into a separate form named Dealer. What built-in will you use?
A . ADD_PARAMETER
B . SET_APPLICATION_PROPERTY
C . WRITE_VALUE
D*. COPY
E . NAME_IN
Explanation:
COPY
This question requires the use of form bind variables, which cannot be referenced directly across modules. The built-ins NAME_IN and COPY are used to read and write values across modules with form bind variables. In this case, COPY is the right choice, because you wish to place values in another field, rather than read them from the field.
4. You have added an LOV to a form and now want to add code to determine whether the user has made a choice from the LOV or dismissed it. What built-in will help you?
A . WHEN-LIST-CHANGED
B . GET_LOV_PROPERTY
C . WHEN-LIST-ACTIVATED
D . POST-TEXT-ITEM
E*. SHOW_LOV
Explanation:
SHOW_LOV
The SHOW_LOV built-in has the ability to display an object (an LOV), and also return a Boolean value to the calling program indicating whether or not the user selected a value from the LOV. If you selected one of the WHEN- or POST- choices, be sure to reread the chapter before the exam...those are triggers, not built-ins.
5. Which of the following allows you to collect objects and easily reuse them in other forms?
A*. Object group
B . Trigger library
C . PL/SQL Library
D . Object package
E . Property class
Explanation:
Object group
Review the section "Grouping Related Items for Reuse" if you need a refresher on this topic.
6. You have created a client-lookup canvas, complete with code and all the necessary objects, that has proven popular enough that others want to use it in their applications. How can you make it available to the other applications from one central source point?
A . Copy the form module into a PL/SQL library.
B . Copy the canvas, code, and objects into a PL/SQL library.
C*. Copy the canvas, code, and objects into an object library.
D . Copy the form module into an object library.
E . Place the canvas, code, and objects into an object group that the other developers will reference.
Explanation:
Copy the canvas, code, and objects into an object library.
Review the section "Reusing Objects from an Object Library" if you need a refresher on this topic.
7. You have inherited an application from a developer who left to pursue a career in music. While looking through the SALARY item's Property Palette, you notice that to the left of its Data Type property is an arrow with an "X" at its point. What does this symbol indicate?
A . The setting has been derived from a Visual Attributes group, but has been overridden.
B . The setting has been derived from a Visual Attributes group.
C . The setting for this property is invalid.
D . The setting has been derived from a property class.
E*. The setting has been derived from a property class, but has been overridden.
Explanation:
The setting has been derived from a property class, but has
been overridden.
A Data Type property can only be derived from a property class. The arrow indicates that this has been done. The "X" at its point indicates that the setting inherited from the property class has been manually overridden for this item.
8. You want to read the value in an item on another form and use it in your current form. What built-in will you use?
A . FIND_ITEM
B . NAME_IN
C . SET_ITEM_PROPERTY
D . GET_ITEM_VALUE
E*. COPY
Explanation:
NAME_IN
Some of the built-in names offered as choices don't exist. Of the ones that do, NAME_IN and COPY are used to read and write values from/to items in other form modules. In this case, NAME_IN is the right choice, because you wish to read a value in another field.
9. You create a module with two forms: Employee and Product. The application allows users to have the forms open simultaneously. The users notice that when they save an Employee record, any unsaved Product records are also committed; the reverse is also true. This is not the behavior they want. What can you do to change it?
A . Open the first form using the OPEN_FORM built-in with the ACTIVATE option.
B . Open the first form using the OPEN_FORM built-in with the SESSION option.
C*. Open the second form using the OPEN_FORM built-in with the SESSION option.
D . Open the second form using the GO_FORM built-in with the ACTIVATE option.
E . Open the second form using the GO_FORM built-in with the NO_ACTIVATE option.
Explanation:
Open the second form using the OPEN_FORM built-in with the SESSION option.
Review the section "Calling One Form from Another" if you need a refresher on this topic.
10. You need a built-in that will copy a value into a global variable and create the variable if it is undefined. What built-in has this ability?
A*. DEFAULT_VALUE
B . SET_VAR
C . COPY
D . CREATE_VAR
Explanation:
DEFAULT_VALUE
Review the section "Built-In Subprograms that Assist Flexible Coding" if you need a refresher on this topic.
11. You are writing versatile code that checks whether your Employee form's Salary field is visible; if it is, the code hides it; if it isn't, the code shows it. What built-in can you use to determine which route the code will take?
A*. GET_ITEM_PROPERTY
B . GET_BLOCK_PROPERTY
C . GET_FORM_PROPERTY
D . GET_WINDOW_PROPERTY
E . GET_RECORD_PROPERTY
Explanation:
GET_ITEM_PROPERTY
Visibility is an item-level property, so you would use the GET_ITEM_PROPERTY to determine the current status.
12. You want to use a single multipage tab canvas for different purposes. Which built-in lets you set the labels for the pages dynamically when the application is running?
A . SET_PAGE_PROPERTY
B . SET_CANVAS_PROPERTY
C . SET_TAB_PROPERTY
D*. SET_TAB_PAGE_PROPERTY
Explanation:
SET_TAB_PAGE_PROPERTY
Review the section titled "Built-In Subprograms that Assist Flexible Coding" if you need a refresher on this topic.
13. Which built-in enables you to change window properties dynamically while the application is running?
A*. SET_WINDOW_PROPERTY
B . SET_VIEW_PROPERTY
C . GET_CANVAS_PROPERTY
D . GET_WINDOW_PROPERTY
E . SET_CANVAS_PROPERTY
Explanation:
SET_WINDOW_PROPERTY
14. At what object level do you place WHEN-WINDOW- triggers?
A*. Form
B . Canvas
C . Block
D . Window
Explanation:
Form
Windows do not have the capability to hold triggers, so you need to define a WHEN-WINDOWS- trigger one level higher in the object hierarchy: the form level.
15. What happens to a function key's default functionality when you define a key trigger for the function key?
A . The default functionality overrides whatever code is contained in the key trigger.
B . The default functionality is augmented by whatever code is contained in the key trigger.
C*. The default functionality is replaced by whatever code is contained in the key trigger.
D . Forms determines each time the function key is pressed whether it should execute the default functionality or the key trigger.
Explanation:
The default functionality is replaced by whatever code is contained in the key trigger.
16. Which property and setting will prohibit the user from deleting a master record if related detail records exist?
A . Relation property Delete Record Behavior set to Cascading
B . Master block property Delete Record Behavior set to Non Isolated
C . Master block property Delete Record Behavior set to Cascading
D*. Relation property Delete Record Behavior set to Non Isolated
E . Master block property Delete Record Behavior set to Isolated
Explanation:
Relation property Delete Record Behavior set to Non Isolated
17. What trigger can institute a default functionality, or no functionality, for every function key that does not have an explicit trigger?
A . KEY-ELSE
B . KEY-FUNCTION
C . KEY-Fn
D*. KEY-OTHERS
E . KEY-NONE
Explanation:
KEY-OTHERS
The purpose of the KEY-OTHERS command is to replace the functionality of any key that can have a trigger assigned to it but does not.
18. What built-in gives you the ability to change the cursor's appearance dynamically?
A*. SET_APPLICATION_PROPERTY
B . SET_CANVAS_PROPERTY
C . SET_CONTEXT
D . SET_ITEM_PROPERTY
E . SET_FORM_PROPERTY
Explanation:
SET_APPLICATION_PROPERTY
19. What built-in enables you to dynamically control when a detail block is populated?
A . SET_BLOCK_PROPERTY
B*. SET_RELATION_PROPERTY
C . SET_ITEM_PROPERTY
D . SET_WINDOW_PROPERTY
Explanation:
SET_RELATION_PROPERTY
20. What trigger is necessary for implementing a cascading delete in a master/detail relation?
A . PRE-CASCADE
B . PRE-POST
C*. PRE-DELETE
D . PRE-UPDATE
E . POST-CASCADE
Explanation:
PRE-DELETE
The PRE-DELETE trigger is the only one that has the capability to intercept a master-record deletion, check to determine if related detail records exist, and delete those detail records before proceeding to delete the master record. A PRE-CASCADE, POST-CASCADE, or PRE-POST trigger do not exist.
21. You need to add a display item to a form. The item will display a calculated total summarizing data from several different tables. You do not want to create any new objects in the database. What is the best course of action to take?
A . Using the Data Block Wizard, create a block with a stored procedure as its data source type.
B . Using the Data Block Wizard, create a block with a view as its data source type.
C . After creating a data block manually, set its Query Data Source Columns property to the desired columns and write the appropriate select command in its Query Data Source Arguments property.
D*. After creating a data block manually, set its Query Data Source Type to FROM clause query, and write the appropriate select command in its Query Data Source Name property.
Explanation:
After creating a data block manually, set its Query Data Source Type to FROM clause query and write the appropriate select command in its Query Data Source Name property. You cannot use a stored procedure or a view because both of these require adding a new item to the database. The correct approach is using a FROM clause query.
22. What built-in enables you to replace the query associated with a record group?
A*. POPULATE_GROUP_WITH_QUERY
B . CREATE_GROUP
C . ADD_GROUP_ROW
D . SET_GROUP_QUERY
Explanation:
POPULATE_GROUP_WITH_QUERY
23. What built-in can you use to open a second form modally?
A . OPEN_FORM
B*. CALL_FORM
C . NEW_FORM
D . RUN_PRODUCT
Explanation:
CALL_FORM
CALL_FORM is the built-in that opens forms in a modal window.
24. What built-in can provide the name of the current form?
A*. GET_APPLICATION_PROPERTY
B . GET_BLOCK_PROPERTY
C . GET_WINDOW_PROPERTY
D . GET_FORM_PROPERTY
Explanation:
GET_APPLICATION_PROPERTY
25. What built-in can populate a dynamic list item on a form with values from a record group?
A*. POPULATE_LIST
B . POPULATE_LIST_WITH_QUERY
C . SET_LIST_VALUES
D . RETRIEVE_LIST
Explanation:
POPULATE_LIST
26. What built-in enables you to change a nonquery record group into a query record group?
A . POPULATE_GROUP
B . CREATE_GROUP_FROM_QUERY
C*. POPULATE_GROUP_WITH_QUERY
D . POPULATE_LIST_WITH_QUERY
Explanation:
POPULATE_GROUP_WITH_QUERY
The purpose of the POPULATE_GROUP_WITH_QUERY built-in is to fill a record group with data based on a given query, even if the record group was originally a nonquery group.
27. How can you base a data block on a stored procedure that uses a ref cursor?
A . Using the Data Block Wizard, specify a data source type of table.
B*. Using the Data Block Wizard, specify a data source type of stored procedure.
C . After creating a data block manually, set the Query Data Source Name property to the appropriate stored procedure.
D . After creating a data block manually, set the Query Data Source Columns property to the appropriate stored procedure.
Explanation:
Using the Data Block Wizard, specify a data source type of stored procedure.
The options detailing the creation of a data block manually specify using the name of the stored procedure in properties not designed to hold a procedure name. Using the Data Block Wizard, you do not have to specify a data source type of table when you also have the option for stored procedure.
28. Name a benefit of using a FROM clause query as the basis for a data block.
A . Can perform server joins, calculations, and lookups without needing specific access rights to tables
B . Can utilize any PL/SQL code
C*. Can perform server joins, calculations, and lookups without needing to create a view
D . Can include user-defined parameters
Explanation:
Can perform server joins, calculations, and lookups without needing to create a view
The essence of the FROM clause query is its capability to nest SQL select statements in subqueries that perform lookups, table joins, and calculations without relying on a database view.
29. What built-in enables you to populate a record group with data that can be filtered dynamically at runtime?
A . CREATE_GROUP_FROM_PARAMETER
B . POPULATE_LIST
C*. POPULATE_GROUP
D . SET_GROUP_FILTER
Explanation:
POPULATE_GROUP
30. You have created a sales application that uses one form for the sales ticket and a second form to list the items being purchased. When the second form is called, the sales ticket is still open and has pending changes. What mode will the second form be opened in?
A*. Post-only mode
B . Commit mode
C . Enter-query mode
D . Open-transaction mode
Explanation:
Post-only mode
31. What built-in enables you to change the contents of a static record group at runtime?
A . POPULATE_GROUP_FROM_QUERY
B . POPULATE_GROUP
C . ADD_GROUP_ROW
D*. You cannot change the contents of a static record group at runtime.
Explanation:
You cannot change the contents of a static record group at runtime.
The definition of a static group is one whose contents cannot be changed at runtime.
32. What built-in enables you to pass data from a record group to a separate Oracle graph?
A . PASS_GROUP_DATA
B*. RUN_PRODUCT
C . OPEN_REPORT_WITH_GROUP
D . PASS_GROUP
Explanation:
RUN_PRODUCT
The RUN_PRODUCT built-in is designed to open other forms of graphics in their respective runtime programs.
33. When you need to design a pair of forms in which one passes values to the other, when and where should you define the parameters that will accept the values?
A*. In the called form, at design time
B . In the calling form, at design time
C . In the calling form, at runtime
D . In the called form, at runtime
Explanation:
In the called form, at design time
A parameter that is to be received must be defined at design time, and of course, it must be defined in the called form. See the section titled "Passing Data Between Forms Using Parameter Lists" for a refresher on this topic.
34. What reusable component enables you to lead your users through complicated processes?
A . Navigator class
B . ActiveX controls
C . Standard Object library
D . Picklist class
E*. Wizard class
Explanation:
Wizard class
The Wizard class enables you to create your own custom wizards, which can lead users through complicated processes.
35. What reusable component enables you to create an Object Navigator-like interface for your own applications?
A . Picklist class
B . ActiveX controls
C . Calendar class
D*. Navigator class
E . Standard Object library
Wizard class
Explanation:
Navigator class
The Navigator class contains objects that make it easy to implement a Navigator interface in your own applications.
36. What built-in enables you to find the internal ID of a timer?
A*. FIND_TIMER
B . WHEN-TIMER-EXPIRED
C . SET_TIMER
D . CREATE_TIMER
E . SET_TIMER_PROPERTY
Explanation:
FIND_TIMER
The FIND_TIMER built-in returns the internal ID of whatever timer's name is provided as an argument.
37. What reusable component enables you to create a customized SmartClass?
A . Picklist class
B . ActiveX controls
C . Calendar class
D . Navigator class
E*. Standard Object library
Explanation:
Standard Object library
38. What built-in enables you to eliminate a timer?
A*. DELETE_TIMER
B . REMOVE_TIMER
C . FIND_TIMER
D . SET_TIMER
E . SET_TIMER_PROPERTY
Explanation:
DELETE_TIMER
The DELETE_TIMER built-in's sole purpose is to deactivate and eliminate timers. A REMOVE_TIMER built-in does not exist.
39. You moved a number of your application's program units over to the server and started experiencing DBMS errors. What built-in can you use to capture these errors and the information they return?
A . DBMS_ERROR
B . DBMS_ERROR_NUM
C . DBMS_ERROR_STRING
D*. DBMS_ERROR_TEXT
Explanation:
DBMS_ERROR_TEXT
The DBMS_ERROR_TEXT built-in is designed specifically to return the text of error messages sent back by the database server.
40. What trigger is used to respond to timers, and at what level is it most commonly defined?
A . WHEN-TIMER-BEGINS at the block level
B . ON-TIMER at the window level
C . ON-TIMER-EXPIRE at the form level
D . ON-TIMER-BEGIN at the block level
E*. WHEN-TIMER-EXPIRED at the form level
Explanation:
WHEN-TIMER-EXPIRED at the form level
41. What trigger should you use to activate a calendar when the user presses the List of Values function key while in a date field?
A . WHEN-LOV-OPEN
B . ON-LIST-OPEN
C . KEY-LIST-OPEN
D . ON-LISTVAL
E*. KEY-LISTVAL
Explanation:
KEY-LISTVAL
The KEY-LISTVAL trigger fires whenever the user presses the LOV function key.
42. What are the steps for embedding an existing chart on a form that is open in the Layout Editor?
A . Execute the File | Import menu command, identify the chart file, and move the resulting chart to the correct position on the canvas.
B . Invoke the Chart Wizard, identify the chart file, and move the resulting chart to the correct position on the canvas.
C*. Create a chart item manually using the Chart Item button, identify the chart file in the item's Property Palette, and move the resulting chart to the correct position on the canvas.
Explanation:
Create a chart item manually using the Chart Item button, identify the chart file in the item's Property Palette, and move the resulting chart to the correct position on the canvas.
The Chart Wizard is only useful for creating new charts, so it is not a correct answer because the question specifies that you are dealing with an existing chart. The command File | Import does not exist in Form Builder. When dealing with an existing chart file, you bypass the Chart Wizard, create a new chart item manually, and alter the new item's properties to use the existing chart file.
43. What built-in enables you to manipulate table structures at runtime?
A . DDL_RUNTIME
B*. FORMS_DDL
C . RUNTIME_DDL
D . DDL_FORMS
E . FORMS_RUNTIME
Explanation:
FORMS_DDL
The FORMS_DDL built-in gives you the ability to execute SQL commands during runtime. All other potential answers to this question were made up (FORMS_RUNTIME is a program, not a built-in).
44. What built-in enables you to determine which timer fired a WHEN-TIMER-EXPIRED trigger?
A*. GET_APPLICATION_PROPERTY
B . GET_TIMER_PROPERTY
C . SYSTEM.TIMER
D . FIND_TIMER
Explanation:
GET_APPLICATION_PROPERTY
45. What file format must a third-party external procedure be in for Forms 6i to use it?
A . PL/SQL8
B*. DLL
C . C++
D . Structured Query Language
Explanation:
DLL
An external procedure can be written in a variety of third-party languages, but it must be stored in the .dll format in order for Forms 6i to use it.
46. What is the return data types of id_null, show_lov
A. Returns a Integer value.
B. Returns a char value
C. * Returns a Boolean value
D. None of the above
Explanation:
Returns a Boolean value
47. What is the order of firing the following triggers((Both are in form-level))
1. when-new-form-instance
2. pre-text-item
A. *Pre-Text , when-new-form-instance
B. When-new-form-instance, pre-text-item
C. None of the above
Explanation:
Pre-Text , when-new-form-instance
48. Difference between Post Query and Pre Query.
A. Post Query fires only once, Pre Query fires for each return row.
B. When Post Query fires, Pre Query returns more than one row.
C. *Post Query fires once for each record fetched from the query Pre Query fires only once.
D. None of the above
Explanation:
Post Query fires once for each record fetched from the query Pre Query fires only once.
49. What is the sequence of triggers firing?
Pre-form, post-form, when-new-form-instance, pre-text-item, pre-block, pre-record.
A. Pre-form, pre-record, pre-block, pre-text-item, post-form, when-new-form-instance
B. Pre-form, pre-block, pre-record, pre-text-item, post-form, when-new-form-instance
C. Pre-form, When-new-form-instance, pre-block, pre-record, pre-text-item, post-form
D. *Pre-form, pre-block, pre-record , pre-text-item, When-new-form-instance, post-form.
Explanation:
Pre-form, pre-block, pre-record , pre-text-item, When-new-form-instance, post-form.
50. What is the validation unit property of form module?
A. *Record_Scope, Item_Scope, Block_Scope, Default_Scope
B. Data_Scope, Trigger_Scope
C. Static_Scope, Dynamic_Scope
D. None of the above
Explanation:
Record_Scope, Item_Scope, Block_Scope, Default_Scope
Validation unit property of form module is
Record_Scope, Item_Scope, Block_Scope, Default_Scope and Form_Scope
1. You open a single property sheet to display properties for your DEPARTMENT data block and DEPARTMENT canvas simultaneously. Which Property Palette display mode is likely to show more properties?
A . Intersection
B*. Union
Explanation:
Union
The Intersection display mode shows only the properties that multiple selected objects have in common, while the Union display mode shows all properties for all selected objects, whether the objects share the properties in common or not.
2. What does it mean when the Property Palette displays ***** as a property's value?
A*. Two or more objects are selected, and their values for that property are not the same.
B . The value "*****" will be inserted into the field automatically.
C . You cannot update that property for the object you have selected.
D . The property is not applicable for the object you have selected.
Explanation:
Two or more objects are selected, and their values for that property are not the same
Because the Property Palette cannot display more than one value per property, the only way it can deal with multiple objects is to display something special when those objects' values are different. The special display is *****.
3. What happens if you select multiple objects, open the Property Palette, and change a property's value?
A . The changed value displays as *****.
B . The Property Palette shows each object's old and new values for that property.
C*. The change is applied to all selected objects.
D . You cannot change a property for multiple objects at one time.
Explanation:
The change is applied to all selected objects
4. Which data block property would you consider changing if your records include LONG items that are not likely to be edited?
A*. Update Changed Columns Only
B . Update Allowed
C . Query Allowed
D . DML Array Size
Explanation:
Update Changed Columns Only
If your records include LONG items that are not likely to be edited, this data block property can improve application performance by keeping the application from sending the voluminous LONG data back to the server during an update command.
5. What does the Property Palette toolbar field labeled Find do?
A . Locates other objects containing the same property as the one you currently have selected
B . Allows you to search-and-replace a given property value with a different value
C . Locates Form Builder files on your hard disk
D*. Forces the Palette to place its focus on the first property matching the characters you type
Explanation:
Forces the Palette to place its focus on the first property matching the characters you type
The Property Palette toolbar field labeled Find makes the Property Palette quickly jump to specific properties. If the group containing the matching property is closed, the Find field will even open it up for you.
6. What would be the result of completely deleting a data block from the Object Navigator?
A . The data blocks and components are deleted but can be retrieved using the Edit | Undo command.
B . The data blocks and components are irreversibly deleted, and all components from the data block are removed from any canvas that contained them, including the data block's frame and boilerplate title text.
C*. The data blocks and components are irreversibly deleted, and all components from the data block are removed from any canvas that contained them, but the data block's frame and boilerplate title text will stay on the canvas.
D . The data blocks and components are irreversibly deleted, and all components from the data block stay on the canvas and must be deleted manually.
Explanation:
The data blocks and components are irreversibly deleted, all components from the data block are removed from any canvas that contained them, but the data block's frame and boilerplate title text will stay on the canvas.
7. What does the Property Palette context bar do?
A . Nothing
B*. Identifies which object's properties are currently being displayed by the Property Palette
C . Identifies which program you are in when you open the Property Palette
D . Provides help instructions based on your location in the Property Palette
Explanation:
Identifies which object's properties are currently being displayed by the Property Palette.
8. Which of the following occur if you copy multiple properties from one object and paste them into another?
A*. No Answer is Correct
B . Properties not relevant to the destination object will be added to that object.
C . Properties with blank properties will be pasted.
D . It is not possible to copy multiple properties at one time.
E . If the destination is a different type of object than the source, the destination object will be changed to the same type of object as the source.
Explanation:
No Answer is Correct
The Property Palette can copy and paste individual or multiple properties. When copying multiple properties, the Palette pastes only the properties for which an actual value is shown, and only the properties that are relevant to the object receiving the pasted properties.
9. You created an LOV for stock items and included a Quantity Currently In Stock column in the LOV. How can you ensure that the user sees accurate "in stock" numbers each time the LOV is invoked?
A . There is no way to ensure this.
B . Programmatically requery all tables in the application when the user opens that canvas.
C*. Enable the LOV's Automatic Refresh property.
D . Enable the LOV's Automatic Select property.
Explanation:
Enable the LOV's Automatic Refresh property
The Automatic Refresh property determines whether the LOV's underlying query executes every time the LOV is invoked, or only the first time it is invoked. Setting the property to Yes configures it to requery every time.
10. You have created a SALES_TICKET form for a point-of-sale application. You now want to modify the Transaction_Date_Time item in the form so it is automatically populated with the current date and time each time a new record is created. How can you accomplish this?
A . Set the Default Value property to SYSDATE.
B . Set the Initial Value property to SYSDATE.
C . Set the Default Value property to $$DATETIME$$.
D*. Set the Initial Value property to $$DATETIME$$.
Explanation:
Set the Initial Value property to $$DATETIME$$.
The is no Item property called Default Value, and while SYSDATE is a valid parameter in a SQL query, it will not work in the Initial Value property; you must use $$DATETIME$$.
11. What does freezing the Property Palette do?
A . Enables you to change a property in multiple objects at one time
B . When multiple objects are selected, shows only those properties that all selected objects share in common
C*. Forces the Palette to continue displaying properties for the currently selected object(s), regardless of what object(s) you select from that point on
D . Opens a second Palette for comparing multiple objects' properties
Explanation:
Forces the Palette to continue displaying properties for the currently selected object(s), regardless of what object(s) you select from that point on
12. What is the best way to ensure that an item cannot accept query criteria?
A . Set the item's Query Length property to 0.
B . Set the item's Queryable property to No.
C*. Set the item's Query Allowed property to No.
D . Set the item's Disable Query property to Yes.
Explanation:
Set the item's Query Allowed property to No
There are no properties named Disable Query or Queryable. Setting the Query Length property to 0 simply tells Oracle Forms 6i to use the item's length as the maximum query length.
13. How many characters would you need to type in an LOV to select the WHEN-KEY-UP item from a list containing WHEN-BUTTON-PRESSED, WHEN-KEY-DOWN, and WHEN-KEY-UP, assuming they are the only items in the list and the LOV's properties are set to automatically display the LOV and automatically enter the value once a row is selected?
A . 3 characters
B . 1 character
C*. 2 characters
D . 10 characters
Explanation:
2 characters
Because all three choices begin with "WHEN-," the LOV only cares about the first differentiating character, which is the "K" that identifies the KEY group. The next character needed is the "D" to select DOWN, after which the row's key value will automatically be entered into the text item.
14. What is the definition of the term "text item"?
A . Any control on your form that allows the user to view and edit text, numbers, or dates
B . Any control on your form that allows the user to view and edit text
C . Any control on your form that allows the user to view and edit text or numbers
D . The label preceding a field on a form
E*. Any control on your form that allows the user to view and edit text, numbers, dates, or long data
Explanation:
Any control on your form that allows the user to view and edit text, numbers, dates, or long data
15. You have created an LOV for a text item on your canvas, and you would like the LOV to appear automatically each time the user enters that text item. What is required to make that happen?
A . Set the Automatic Select property in the LOV Property Palette to Yes.
B*. Set the Automatic Display property in the LOV Property Palette to Yes.
C . Set the Automatic Refresh property in the text item Property Palette to Yes.
D . Set the Automatic Refresh property in the LOV Property Palette to Yes.
E . Set the Automatic Display property in the text item Property Palette to Yes.
Explanation:
Set the Automatic Display property in the LOV Property Palette to Yes.
No text item property would effect this change. Of the LOV properties listed, Automatic Refresh determines whether the LOV's contents are requeried each time it is opened, and Automatic Select specifies whether the selected LOV row is placed into the specified text item without the user having to double-click on the row or click the OK button.
16. Which of the following actions can a user do with a display item?
A . Delete existing database values.
B . Update existing database values.
C*. View existing database values.
D . Insert new database values.
E . All Answers are Correct
Explanation:
View existing database values
A display item shows data but does not allow the user to change it. In essence, it is a read-only field.
17. To which of the following items does a control block directly correspond?
A . All Answers are Correct
B . Database
C*. No answer is correct
D . Table
E . Column
Explanation:
No answer is correct
A control block is not associated with a database object. Instead, it contains either controls (such as buttons), or a group of items with single values (such as calculated subtotals).
18. When a control block is created, what items does it contain?
A . None, because, you cannot put items in a control block.
B . Text items for all columns in the related database table.
C*. None. You must manually create any items that will go into a control block.
Explanation:
None. You must manually create any items that will go into a control block.
By definition, a control block is not related to a database table. And you can put items into a control block-that is what it's for. But you must do it manually after the block is created.
19. What is the definition of an input item?
A . A form object through which the user can view data
B . A dialog box
C . A graphics element affecting how a chart will look
D*. A form object through which the user can enter and change data
E . A form object through which the program can enter and change data
Explanation:
A form object through which the user can enter and change data
Input items are the basis of forms-they enable a user to add or edit data. A dialog box may contain input items, but the dialog itself is a window, not an input item.
20. Users of your application have requested that they be able to see STOCK and CUSTOMER canvases on the screen simultaneously. You add a second window to the application. How can you make the CUSTOMER canvas use the second window?
A . Change the window's Primary Canvas property.
B . Change the canvas's Visual Attributes group.
C*. Change the canvas's Window property.
D . It is not possible to change a canvas's display window.
Explanation:
Change the canvas's Window property
A canvas's Window property determines which window the canvas is visible in. The Visual Attributes Group has no window selection properties, and a window's Primary Canvas property specifies the primary canvas for a window that displays multiple canvases.
21. Which check box property controls the text that displays next to the check box?
A*. Label
B . Text
C . Name
D . A check box's text is fixed and cannot be changed.
Explanation:
Label
Remember that both Prompt and Label can place text next to a radio button.
22. Which type of canvas is best suited for displaying tutorial text on the same canvas as the form about which the user is being taught?
A . Tab
B . Viewport
C*. Stacked
D . Toolbar
E . Content
Explanation:
Stacked
The requirement that the tutorial text be visible on the same form limits the choices to either stacked or tab. A tab canvas might be useful for a multipage tutorial, but the requirements did not state the need for multiple pages, so a simple stacked canvas will fulfill the requirement.
23. You are working with an existing radio group in the Layout Editor and try to add a radio button to the group. The Layout Editor responds by:
A . Displaying a warning message, and then returning you to the Layout Editor
B . Offering to create a check box instead, since a radio button group already exists
C*. Presenting a dialog box giving you the chance to select a radio group for the new radio button, or create a new radio group for it
Explanation:
Presenting a dialog box giving you the chance to select a radio group for the new radio button, or create a new radio group for it
The Layout Editor is willing to add buttons to an existing radio group. It just needs to know which group will get the new button, or if a completely new group is what you desire.
24. Your Employee form includes a SALARY text item. You want to ensure that standard users cannot input or change a salary value, but you want the value to look exactly like a regular field. What is the best way to do this?
A . Set the item's Enabled property to No, and its Update Allowed property to No.
B*. Set the item's Insert Allowed property to No, and its Update Allowed property to No.
C . Set the item's Enabled property to No.
D . It is not possible for an unchangeable item to look like a changeable item.
Explanation:
Set the item's Insert Allowed property to No, and its Update Allowed property to No
Changing an item's Enabled property to No causes its contents to display with light gray characters instead of black. Therefore, this is the only valid choice.
25. What type of canvas can easily eliminate the need for a menu in your application?
A*. Toolbar
B . Content
C . Tab
D . Stacked
Explanation:
Toolbar
A toolbar canvas's sole purpose is holding buttons that initiate actions. The buttons can replace every menu action your users would need to take.
26. The DEPARTMENT table in your database has been augmented with a BUDGET column. You want to add BUDGET as an item on your Department form, but the item should be a read-only text box so users cannot change it. The best way to do this is:
A . In the Layout Editor, create a display item and set its Insert Allowed property to No, its Update Allowed property to No, and its Database Item property to No.
B . In the Data Block Wizard, move the BUDGET column into the Available Items area. Change the new data block item's Insert Allowed and Update Allowed properties to No. Proceed to the Layout Editor and add BUDGET as a text item.
C . In the Data Block Wizard, move the BUDGET column into the Available Items are C:
Proceed to the Layout Editor and add BUDGET as a text item, and change the item's Insert Allowed and Update Allowed properties to No.
D*. In the Layout Editor, create a display item and set its Column Name property to BUDGET.
Explanation:
In the Layout Editor, create a display item and set its Column Name property to BUDGET.
Setting an item's Database Item property to No keeps it from retrieving database data, eliminates two answers, but it creates a normal-looking text box that actually allows the user to type in data; it isn't until the user tries to save their work that the data block's Insert Allowed and Update Allowed properties halt the action. This is not optimal design. The third incorrect answer creates an application in which the field's data cannot be changed, but the user can still place focus on the field, which is also not optimal.
27. You have created a form that contains two canvases, ten database items, and four buttons. The items have all been placed into a group, and the buttons have been placed into a separate group. What happens when you click one of the buttons in the Layout Editor?
A*. The group of buttons is selected.
B . Nothing is selected.
C . All groups are selected
D . The button is selected.
E . All items on the button's canvas are selected
Explanation:
The group of buttons is selected.
The primary reason for groups is to ensure that when any item in the group is selected, all items are selected with it.
28. Which canvas type is most dissimilar to the others?
A . Content
B . Stacked
C . Tab
D*. Toolbar
Explanation:
Toolbar
Content, stacked, and tab canvases are all intended to display database data. The toolbar canvas type is not; it is intended to display buttons that work in concert with the items on the other three canvas types.
29. What is the primary difference between tab and stacked canvases?
A . A stacked canvas can contain push buttons.
B . A stacked canvas obscures what is beneath it.
C*. A tab canvas can contain multiple pages.
D . A tab canvas looks much cooler.
Explanation:
A tab canvas can contain multiple pages.
The essence of a tab canvas is the fact that it consists of multiple pages of data, each page overlaying the others when it is selected by the user or developer. It is not possible to get this functionality from a single stacked canvas.
30. What trigger would you use to execute code each time a user modifies the value of a check box?
A . ON-NEW-CHECKBOX-INSTANCE
B . WHEN-CHECKBOX-UNCHECKED
C . WHEN-CHECKBOX-CLICKED
D . WHEN-CHECKBOX-CHECKED
E*. WHEN-CHECKBOX-CHANGED
Explanation:
WHEN-CHECKBOX-CHANGED
31. You would like to create a trigger that fires each time a window is closed by the user. You will most likely place the trigger at which of the following levels:
A . Canvas level
B . Window level
C . Data block level
D . Item level
E*. Form level
Explanation:
Form level
Windows do not have triggers. Placing the WHEN-WINDOW-CLOSED trigger at the Form level allows it to fire when any window in the module is closed.
32. What trigger would fire each time a new record is created?
A . ON-NEW-RECORD
B*. WHEN-NEW-RECORD-INSTANCE
C . WHEN-VALIDATE-RECORD
D . WHEN-DATABASE-RECORD
Explanation:
WHEN-NEW-RECORD-INSTANCE
ON-NEW-RECORD is not a valid trigger name. Choices WHEN-VALIDATE-RECORD and WHEN-DATABASE-RECORD fire at other times. Review the section "Supplementing the Functionality of Input Items" if you need a reminder on this topic.
33. What do you need to do to within Form Builder to run a form module in debug mode?
A . Enable Debug Messages and then run your form. The Debugger will appear automatically.
B*. Enable the Debug Mode button, run the form, and the Debugger displays automatically.
C . Run the form, and in the Forms Runtime program execute the Help | Debug menu command.
D . Enable the Debug Mode button, run your form, and in the Forms Runtime program execute the Help | Debug menu command.
Explanation:
Enable the Debug Mode button, run the form, and the Debugger displays automatically.
See the section "Running a Form Module in Debug Mode" for a refresher on this topic.
34. When does the PRE-QUERY trigger fire?
A*. After the user enters query criteria, but before the query executes
B . Before the form enters Enter-Query mode
C . After the form enters Enter-Query mode, but before the user enters query criteria
D . After the query executes, but before records are shown to the user
Explanation:
After the user enters query criteria, but before the query executes
The PRE-QUERY trigger fires after Enter-Query mode but before a query's select statement has been finalized, and therefore before the query is executed.
35. Which built-in causes an editor to display for a text item?
A . WHEN-NEW-ITEM-INSTANCE
B . SHOW-EDITOR
C*. SHOW_EDITOR
Explanation:
SHOW_EDITOR
SHOW-EDITOR is formatted as a trigger, not a built-in, and doesn't exist. WHEN-NEW-ITEM-INSTANCE exists but is also a trigger, not a built-in.
36. You want to write a trigger that screens a query condition. At what level will you place the trigger?
A . Block
B*. Form
C . Item
D . Record
Explanation:
Form
37. You wish to have certain values in a form initialized when the form is first opened. What trigger will you use?
A . WHEN-NEW-CANVAS-INSTANCE
B*. WHEN-NEW-FORM-INSTANCE
C . WHEN-NEW-FORM
D . WHEN-FORM-OPENED
E . WHEN-NEW-CANVAS
Explanation:
WHEN-NEW-FORM-INSTANCE
None of the other choices are valid triggers.
38. What part of a trigger specifies the trigger's actions?
A . Type
B . Name
C*. Code
D . Scope
Explanation:
Code
A trigger's actions are defined entirely by its code.
39. Which built-in causes an LOV to display for a text item that has one defined?
A . WHEN-NEW-ITEM-INSTANCE
B . WHEN-NEW-LOV
C . GO_ITEM
D*. SHOW_LOV
Explanation:
SHOW_LOV
WHEN-NEW-ITEM-INSTANCE and WHEN-NEW-LOV are triggers, not built-ins. GO_ITEM navigates to an item but does not open an LOV.
40. What trigger can you use to ensure that a query entered by the user includes at least one item that is indexed, and keep the query from occurring if not?
A*. PRE-QUERY
B . WHEN-CLEAR-BLOCK
C . ON-SELECT
D . POST-SELECT
E . ON-FETCH
Explanation:
PRE-QUERY
While the other triggers listed are query triggers, only the PRE-QUERY trigger fires before the select statement is executed.
41. What is the purpose of the KEY-OTHERS trigger?
A . Provides code to execute if a key's own trigger fails
B*. Provides code to execute if user presses a key that has no trigger attached
C . Provides code to execute if user presses wrong key
D . Provides code that accesses another key's trigger and executes the code it contains
Explanation:
Provides code to execute if user presses a key that has no trigger attached.
See the section "Form Trigger Categories" for a refresher on this topic.
42. Your data analysis application is slowing the network to a crawl. You analyze the queries users are performing and discover that the majority of their queries are too broad, returning many more records than necessary. You decide to require that any query have at least three fields containing criteria. What type of trigger can you use to enforce that requirement?
A . POST-QUERY
B . ON-NEW-QUERY-INSTANCE
C . PRE-UPDATE
D*. PRE-QUERY
E . POST-UPDATE
Explanation:
PRE-QUERY
The PRE-QUERY trigger fires before a query's select statement has been finalized, and is therefore ideal for screening query criteria before the query is executed.
43. You have created an alert with three buttons. What value will be returned if the user selects the second button?
A . BUTTON2
B . DIALOG_BUTTON2
C*. ALERT_BUTTON2
D . It depends on the choice being offered by the button.
Explanation:
ALERT_BUTTON2
44. What is the default level at which validation occurs in the Forms Runtime program?
A*. Item
B . Form
C . Block
D . Record
Explanation:
Item
By default, the Forms Runtime program validates an item immediately when the user tries to leave the item.
45. How does the Forms Runtime program respond when a user enters text into a text item that has an LOV attached and the VALIDATE_FROM_LIST property set to Yes?
A . The Forms Runtime program ignores the LOV if the user types a value directly into the field.
B . The Forms Runtime program populates the item automatically with the first value in the LOV that matches the user's entry.
C*. The Forms Runtime program opens the LOV and shows only items that match what the user has typed so far.
D . Validate From List is a Data Block property, not an Item property.
Explanation:
The Forms Runtime program opens the LOV and shows only items that match what the user has typed so far.
See the section "Introduction to Form Builder Validation Properties" for a refresher on this topic.
46. How can you cause a block to use a database sequence to get unique IDs?
A . Set the Initial Value property to :sequence.sequence-name.nextval.
B . Set the Validate From List property to :sequence.sequence-name.nextval.
C . Set the DML Array Size property to :sequence.sequence-name.nextval.
D*. This action is not possible.
Explanation:
This action is not possible.
Data blocks cannot read sequences, and in fact cannot store values at all. Items, on the other hand, can.
Give yourself half a point if you answered:
Set the Initial Value property to
:sequence.sequence-name.nextval.
which would have been the right answer if the question had referred to an item instead of a block, and remember to pay closer attention to the wording of questions. In some Oracle exam questions, a single word defines why one choice is right and another choice wrong.
47. You have written a contact-tracking application that includes a field for the last date a client was contacted. You want to use a trigger to guarantee that whenever the date in that field is changed, the date entered is later than the date that was there before. What is the best trigger to use?
A . PRE-UPDATE
B . ON-COMMIT
C . ON-UPDATE
D*. PRE-COMMIT
E . POST-UPDATE
Explanation:
PRE-COMMIT
PRE-COMMIT is a form-level trigger that fires only once at the beginning of a transaction, so it cannot perform validation on a row-by-row basis. ON-UPDATE and ON-COMMIT only occur if you have replaced the default Forms Runtime transaction processing. POST-UPDATE occurs after the update has occurred, so it is too late for a validity check. The remaining trigger, PRE-COMMIT, is perfect.
48. Your form module's Validation Unit property is set to Form. The module includes a data block that has a PRE-TEXT-ITEM trigger. At what point will the trigger fire?
A*. Never
B . When data is committed
C . Before the form is validated
D . After the form is validated
Explanation:
Never
The trigger will not fire because the object level defined in the trigger name item is smaller than the module's validation unit.
49. You want to add a delete-confirmation dialog to your application. You can do so by creating which type of object?
A*. Alert
B . Message
C . Editor
D . Message box
Explanation:
Alert
50. You would like to keep the user from seeing the Forms Runtime program's "nn records applied and saved" messages. What would you put in the form's WHEN-NEW-FORM-INSTANCE trigger?
A . :system.message_level := 0;
B . :system.suppress_working := 'TRUE';
C . :system.suppress_working := 'FALSE';
D*. :system.message_level := 5;
Explanation:
:system.message_level := 5;
See the section "Controlling System Messages" for a refresher on this topic.
51. What is the last DML statement processed during a commit transaction?
A*. INSERT
B . UPDATE
C . DELETE
D . POST
Explanation:
INSERT
The post command does not perform a commit. Of the three remaining choices, their processing order is delete, update, and then insert.
52. Which of these built-ins can you use in a PRE-UPDATE trigger?
A . DOWN
B . COMMIT_FORM
C*. No Answer is Correct.
D . All Answers are Correct.
E . GO_ITEM
Explanation:
No Answer is Correct.
Each built-in listed is a navigational built-in, which cannot be used within the navigational trigger PRE-UPDATE.
53. Which navigational built-in will move the focus to a subsequent record and place it on the same item it was on in the original record?
A . NEXT_BLOCK
B . NEXT_ITEM
C*. DOWN
D . The described action is not possible from a single built-in.
Explanation:
DOWN
54. You would like to modify your form so it uses array processing to send DML statements to the server in batches of 50. How would you do this?
A . Set the canvas's DML Array Size property to 50.
B*. Set the data block's DML Array Size property to 50.
C . Set the window's DML Array Size property to 50.
D . Array processing is limited to 25 records per batch.
Explanation:
Set the data block's DML Array Size property to 50.
1. What is the size of Varchar in Oracle 8.0 ?
a. 2000
b. 4000
c. 254
d. none of the above
2. What is the size of Varchar in Oracle 7.0 ?
a. 2000
b. 4000
c. 254
d. none of the above
3. The default value the lpad function takes is
a. a space (¡§ ¡§)
b. an asterisk
c. The default value is not optional
d. None of the above
4. The no. of columns that may be used as composite primary key in oracle 8
a. 8
b. 16
c. 32
d. none of the above
5. which of the following is true about add_months
a. we can pass a numerical value in first parameter
b. we can pass a negative value in second parameter
c. Both a & b
d. None of the above
6. The latest date that can be stored in oracle 8
a. 31st Dec 4012 A.D
b. 31st Dec 4011 A.D
c. Dec 31st ,9999
d. None of the above.
7. What happens when the first date is greater than the second date that is passed to the months_between function in oracle 8.
a. It gives an error
b. It gives a negative value
c. None of the above
8. Regarding the Summary query which of the following is true
a. The order of the base column list in the select statement should be same in the Group by clause.
b. The order of the base column list in the select statement need not be same in the Group by clause.
c. None of the above
9. Regarding the Summary query which of the following is true
a. All the base table columns selected in the select list should be specified in the Group by clause.
b. All the base table columns selected in the select list need not be specified in the Group by clause.
c. None of the above.
10. How do u mask the user from entering irrelevant data ?
a. Synonym
b. View
c. Index
d. sequence
11. What does the length function returns when applied to column of char datatype ?
12. Which of the following is true about the packages ?
a. Package specification should contain return type of a function
b. Package specification need not contain return type of a function
c. Both a & b
d. None of the above
13. If the first parameter is negative, then second parameter
a. need not be negative
b. there is no such restrictions
c. should be positive
d. None of the above.
14. Which of the following is true about procedures
a. The size of the parameter should be mentioned in a procedure.
b. The size of the parameter should not be mentioned in a procedure
c. Both a & b
d. None of the above.
15. ¡§REFERENCING¡¨ in oracle 8
a. used to mention referential integrity
b. used for creating views
c. there is no such word in oracle 8
d. none of the above
16. If you want to restrict the user, to enter the same values that has been stored in other table then what constraint do u use?
a. Entity integrity
b. Referential Integrity
c. Both a & b
d. None of the above
17. Which of the following is true about NULL?
a. when an arithmetic operation is performed on NULL, u will get the result as NULL
b. NULL is same as 0.
c. NULL is same as blank date.
d. None of the above
18. For a DDL statement, which of the following is true
a. A DDL statement is preceded and followed by commit.
b. All the DML statements gets committed even when u get an error after writing DDL statement.
c. Both a & b
d. None of the above.
19. Which of the following is true for update clause?
a. We can update two base tables simultaneously
b. U can use a subquery in SET clause of the UPDATE statement.
c. Both a & b
d. None of the above
20. Which of the following is true for delete?
a. Delete statement can be given without writing where clause.
b. We can delete two tables simultaneously
c. Both a & b
d. None of the above
21. How do u rename a table ?
a. Using alter command
b. Using RENAME
c. Dropping the table and creating once again
d. None of the above.
22. In oracle 7 which of the following is true about manipulating the view
a. View based on two base tables can be manipulated
b. View having a column which contain operation can be manipulated
c. Both a & b
d. None of the above
23. In oracle 8 which of the following is true about manipulating the view
a. View based on two base tables can be manipulated
b. View having a column which contain operation can be manipulated
c. Both a & b
d. None of the above
24. Which of the following is true about packages
a. We can write a procedure in package body which has not been specified in package specification.
b. We cannot write a procedure in package body which has not been specified in package specification.
c. Both a & b
d. None of the above.
25. Which of the following is true about outer joins
a. The outer join symbol should be present on any one side of the join.
b. The outer join symbol may be present on both the sides of the join
c. The outer join return the rows from the two tables that donot have matching records in other table.
d. None of the above
26. Which of the following is true about procedure and a function
a. Procedure should return a value and a function may not return a value
b. A function has to return a value and a procedure don¡¦t have to
c. Both a & b
d. None of the above.
27. What does OFA stands for ?
a. Oracle Flexible Architecture
b. Oracle Financials Applications
c. Optimal Flexible Architecture
d. None of the above
Oracle Questions
„h What is SQL*Plus and where does it come from?
„h How does one use the SQL*Plus utility?
„h What commands can be executed from SQL*Plus?
„h What are the basic SQL*Plus commands?
„h What is AFIEDT.BUF?
„h How does one restore session state in SQL*Plus?
„h What is the difference between @ and @@?
„h What is the difference between & and &&?
„h What is the difference between ! and HOST?
„h What is the difference between ? and HELP?
„h How does one enable the SQL*Plus HELP facility?
„h How can one disable SQL*Plus prompting?
„h How can one trap errors in SQL*Plus?
„h How does one trace SQL statement execution?
„h How can one prevent SQL*Plus connection warning messages?
„h How can uses be prevented from executing devious commands?
„h How can one disable SQL*Plus formatting?
„h Can one send operating system parameters to SQL*Plus?
„h Can one copy tables with LONG columns from one database to another?
„h Where can one get more info about SQL*Plus?
What is SQL*Plus and where does it come from?
SQL*Plus is a command line SQL and PL/SQL language interface and reporting tool that ships with the Oracle Database Client and Server. It can be used interactively or driven from scripts. SQL*Plus is frequently used by DBAs and Developers to interact with the Oracle database.
SQL*Plus's predecessor was called UFI (User Friendly Interface). UFI was included in the first releases of Oracle, its interface was extremely primitive and anything but user friendly.
How does one use the SQL*Plus utility?
Start using SQL*Plus by executing the "sqlplus" command-line utility. Valid options are:
userid/password@db -- Connection details
/nolog -- Do not login to Oracle. You will need to do it yourself.
-s or -silent -- start sqlplus in silent mode. Not recommended for beginners!
@myscript -- Start executing script called "myscript"
Look at this simple example:
sqlplus /nolog
SQL> connect scott/tiger
SQL> select * from tab;
SQL> disconnect
SQL> exit
What commands can be executed from SQL*Plus?
One can enter three kinds of commands from the SQL*Plus command prompt:
1. SQL*Plus commands - SQL*Plus commands are used to set options for SQL*Plus, format reports, edit files, edit the command buffer, and so on. SQL*Plus commands do not interact with the database. These commands do not have to be terminated with a semicolon (;), as is the case with SQL commands. The rest of this page is dedicated to SQL*Plus commands, eg.
SHOW USER
2. SQL commands - for more information see the Oracle SQL FAQ. Eg:
SELECT * FROM TAB;
3. PL/SQL blocks - for more information see the Oracle PLSQL FAQ. Eg:
BEGIN
DBMS_OUTPUT.PUT_LINE('Hello World!');
END;
/
What are the basic SQL*Plus commands?
The following SQL*Plus commands are available:
ACCEPT Get input from the user
DEFINE Declare a variable (short: DEF)
DESCRIBE Lists the attributes of tables and other objects (short: DESC)
EDIT Places you in an editor so you can edit a SQL command (short: ED)
EXIT or QUIT Disconnect from the database and terminate SQL*Plus
GET Retrieves a SQL file and places it into the SQL buffer
HOST Issue an operating system command (short: !)
LIST Displays the last command executed/ command in the SQL buffer (short: L)
PROMPT Display a text string on the screen. Eg prompt Hello World!!!
RUN List and Run the command stored in the SQL buffer (short: /)
SAVE Saves command in the SQL buffer to a file. Eg "save x" will create a script file called x.sql
SET Modify the SQL*Plus environment eg. SET PAGESIZE 23
SHOW Show environment settings (short: SHO). Eg SHOW ALL, SHO PAGESIZE etc.
SPOOL Send output to a file. Eg "spool x" will save STDOUT to a file called x.lst
START Run a SQL script file (short: @)
How does one restore session state in SQL*Plus?
Look at the following example (Oracle8):
SQL> STORE SET filename REPLACE
SQL> (do whatever you like)
SQL> @filename
What is AFIEDT.BUF?
AFIEDT.BUF is the SQL*Plus default edit save file. When you issue the command "ed" or "edit" without arguments, the last SQL or PL/SQL command will be saved to a file called AFIEDT.BUF and opened in the default editor.
In the prehistoric days when SQL*Plus was called UFI, the file name was "ufiedt.buf", short for UFI editing buffer. When new features were added to UFI, it was the initially named Advanced UFI and the filename was changed to "aufiedt.buf" and then to "afiedt.buf". They presumably needed to keep the name short for compatibility with some of the odd operating systems that Oracle supported in those days.
The name "Advanced UFI" was never used officially, as the name was changed to SQL*Plus before this version was released.
You can overwrite the default edit save file name like this:
SET EDITFILE "afiedt.buf"
What is the difference between @ and @@?
The @ (at symbol) is equivalent to the START command and is used to run SQL*Plus command scripts.
A single @ symbol runs the script in your current directory, or one specified with a full or relative path, or one that is found in you SQLPATH or ORACLE_PATH.
@@ will start a sqlplus script that is in the same directory as the script that called it (relative to the directory of the current script). This is normally used for nested command files.
What is the difference between & and &&?
"&" is used to create a temporary substitution variable and will prompt you for a value every time it is referenced.
"&&" is used to create a permanent substitution variable as with the DEFINE command and the OLD_VALUE or NEW_VALUE clauses of a COLUMN statement. Once you have entered a value it will use that value every time the variable is referenced.
Eg: SQL> SELECT * FROM TAB WHERE TNAME LIKE '%&TABLE_NAME.%';
What is the difference between ! and HOST?
Both "!" and "HOST" will execute operating system commands as child processes of SQL*Plus. The difference is that "HOST" will perform variable substitution (& and && symbols), whereas "!" will not. (Note: use "$" under MVS, VMS, and Windows environments, not "!")
What is the difference between ? and HELP?
There is no difference. Both "?" and HELP will read the SYSTEM.HELP table (if available) and shows help text on the screen.
To use the help facility, type HELP followed by the command you need to learn more about. For example, to get help on the SELECT statement, type:
HELP SELECT
How does one enable the SQL*Plus HELP facility?
To enable HELP for SQl*Plus, run the supplied SQL and Loader scritps to create the Help table and to populate it. Look at this Unix example:
cd $ORACLE_HOME/sqlplus/admin/help
sqlplus system/manager @helptbl
sqlplus system/manager @helpindx
sqlldr system/manager control=plushelp.ctl
sqlldr system/manager control=sqlhelp.ctl
sqlldr system/manager control=plshelp.ctl
If the HELP command is not supported on your operating system, you can access the help table with a simple script like this:
HELP.SQL:
select info
from system.help
where upper(topic)=upper('&1')
/
How can one disable SQL*Plus prompting?
If you run a script that contains "&" symbols SQL*Plus thinks that you want to prompt the user for a value. To turn this off:
SET ESCAPE ON
SET ESCAPE ""
SELECT 'You & me' FROM DUAL;
or
SET DEFINE ?
SELECT 'You & me' FROM DUAL;
Note: You can disable substitution variable prompting altogether by issuing the SET DEFINE OFF commmand.
How can one trap errors in SQL*Plus?
Use the "WHENEVER OSERROR ..." to trap operating system errors and the "WHENEVER SQLERROR ..." command to trap SQL and PL/SQL errors. Eg:
SQL> WHENEVER OSERROR EXIT 9
SQL> WHENEVER SQLERROR EXIT SQL.SQLCODE
How does one trace SQL statement execution?
1. Run the PLUSTRCE.SQL script from the SYS database user. This script is located the in $ORACLE_HOME/sqlplus/admin.
2. Create a PLAN_TABLE using the UTLXPLAN.SQL script. This script is in $ORACLE_HOME/rdbms/admin.
3. Use the "SET AUTOTRACE ON" command to trace SQL execution. This will print the result of your query, an explain plan and high level trace information. Look at this example:
SQL> set autotrace on
SQL> select * from dual;
D
-
X
Execution Plan
----------------------------------------------------------
0 SELECT STATEMENT Optimizer=CHOOSE
1 0 TABLE ACCESS (FULL) OF 'DUAL'
Statistics
----------------------------------------------------------
0 recursive calls
2 db block gets
1 consistent gets
0 physical reads
0 redo size
181 bytes sent via SQL*Net to client
256 bytes received via SQL*Net from client
3 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
How can one prevent SQL*Plus connection warning messages?
When I go to SQl*Plus, I get the following errors:
Error accessing PRODUCT_USER_PROFILE
Warning: Product user profile information not loaded!
You may need to run PUPBLD.SQL as SYSTEM
This messages will stop appearing when you create the PRODUCT_USER_PROFILE table in the SYSTEM schema. This is performed by the PUPBLD.SQL script.
Go to the $ORACLE_HOME/sqlplus/admin directory, connect as SYSTEM and run @PUPBLD from the sqlprompt.
How can users be prevented from executing devious commands?
Yes, command authorization is verified against the SYSTEM.PRODUCT_USER_PROFILE table. This table is created by the PUPBLD.SQL script. Note that this table is not used when someone signs on as user SYSTEM.
Eg. to disable all users whose names starts with OPS$ from executing the CONNECT command:
SQL> INSERT INTO SYSTEM.PRODUCT_USER_PROFILE VALUES ('SQL*Plus', 'OPS$%', 'CONNECT', NULL, NULL, 'DISABLED', NULL, NULL);
How can one disable SQL*Plus formatting?
Issue the following SET commands to disable all SQL*Plus formatting:
SET ECHO OFF
SET NEWPAGE 0
SET SPACE 0
SET PAGESIZE 0
SET FEEDBACK OFF
SET HEADING OFF
SET TRIMSPOOL ON
These settings can also be entered on one line, eg.:
SET ECHO OFF NEWPAGE 0 SPACE 0 PAGESIZE 0 FEED OFF HEAD OFF TRIMSPOOL ON
Can one send operating system parameters to SQL*Plus?
One can pass operating system variables to sqlplus using this syntax:
sqlplus username/password @cmdfile.sql var1 var2 var3
Parameter var1 will be mapped to SQL*Plus variable &1, var2 to &2, etc. Look at this example:
sqlplus scott/tiger @x.sql '"test parameter"' dual
Where x.sql consists of:
select '&1' from &2;
exit 5;
Can one copy tables with LONG columns from one database to another?
About the fastest way of copying data between databases and schemas are by using the SQL*Plus COPY statement. Look at this example:
COPY FROM SCOTT/TIGER@LOCAL_DB TO SCOTT/TIGER@REMOTE_DB -
CREATE IMAGE_TABLE USING -
SELECT IMAGE_NO, IMAGE -
FROM IMAGES;
Interview questions:
1.query for self join.
2.deletion of duplicate rows.
3.post query trigger
4.pre query trigger
5.mastere ¡Vdetail relation
6.report triggers
7.report parameters.
8.format triggers in report.
9.order of triggering of when new item instance.
10.
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| How do I create a special trigger? [message #28276 is a reply to message #27446] |
Sun, 14 December 2003 02:29  |
Jürgen Sieke
Messages: 3
Registered: December 2003
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Junior Member |
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My problem: I have a table with a primary key on with a foreign key and references in the same table.
How can I create a trigger "After update ... set :new name ... where :old name ..."? Oracle or ODBC makes problems with referentielle integritiate.
Thank you for response
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| Re: SQL ,PL/SQL & D2K Interview Questions [message #33717 is a reply to message #27446] |
Thu, 28 October 2004 13:33 |
P.Ramana Reddy
Messages: 1
Registered: October 2004
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Junior Member |
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thank you sir , i have been through lot of books, but i did'nt get the correct idea how would be the interview question. But i got the confidence that i can attend the interview after i finish reading the qes that u have given here. this material is very nice.
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