I recently did a comparison caching mechanisms of scalar subquery caching(SSC) and deterministic functions in 11.2. Unfortunately, I do not have enough time to do a full analysis, so I will post it in parts.
1. Both mechanisms are based on hash functions.(About hash tables and hash collisions for scalar subquery caching excelent wrote Tom Kyte and Jonathan Lewis(“Cost-Based Oracle fundamentals” chapter 9))
2. Deterministic caching depends on fetch size(arraysize) – results cached only within one fetch call, ssc has no this limitation.
Oracle Database 12c: New Features – Pluggable Databases by Michael Rajendran
Oracle has leap forwarded the middleware technologies especially the database technology into the cloud. So far Oracle has been the traditional RDBMS database suitable for the private enterprise data centers within corporate walls.
The COST column cannot be used to compare execution plans. Punkt.
We all know that CHAR and VARCHAR2 are two different datatypes used for storing strings in Oracle. When I asked many people about what’s the difference exactly, all were saying VARCHAR2 can be used for variable sized character strings. As I’m not satesfied with the answer, as always, I’ve decided to do my own experiments on these two.
When I was doing a research on Oracle Database creation, through DBCA, last week, I came across a very interesting scenario which I couldn’t stop sharing with you :)
I have a cluster of machines (don’t confuse it with a RAC cluster but just a group of machines required for my application deployment) with 22.214.171.124 installed and a Database instance running.
I got a requirement to remove everything accumulated in the machine as a result of the Oracle installation and the Database creation: The installation directories, the datafiles, oratab entries etc…
After removing all th
Hi Oracle geeks,
Last Friday, I’ve noticed a strange thing happening in my 126.96.36.199 Database: I’m able to create objects in a tablespace which is marked READ ONLY !!!
Don’t believe this??
I have just joined an in flight project and find the lead data modeler has created a name value pair data model.
The reason given was flexibility of data model considering some records can have as many as 900 attributes. The .Net application team seem to be loving it, as they can code everything with very few tables in mind.
I feel the model is difficult to query, difficult to load and difficult to syndicate and in all likelyhood will suffer from poor performance.
I just posted a complete integrated set of tools to manage, monitor and tune the Oracle database.
It is free, no registration or email is required. I will just appreciate any kind of feedback to make it better.
The package comprises the following topics:
This section allows you to view and maintain virtually all database objects, including partitioned tables and materialized views. It also includes a function to view inter-dependency between objects.
This section allows you manage users and security.
Matthew Morris (who makes many constructive and knowledgeable contributions to the forum) has written a series of study guides for the OCA/OCP exams. I asked him if I could have a copy of one to review. The result: it's very good. This is a copy of the review I put up on Amazon.
OS:Red Hat Linux As 5
[=16]In 9i,we open the database with resetlogs just only once when we do the incomplete recover,but in the 10g, it can open the database with resetlogs more than once,the flowing test is show how to open the database with resetlogs many times.