| Differences between Oracle SID / Instance/ Listener / Service or Service_Name / Database [message #302142] |
Sun, 24 February 2008 01:43  |
oraclewannabe
Messages: 26
Registered: January 2008
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Junior Member |
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Hi guys, i am confuse about the following terms above and how they relate to one another when connecting to a database..
This is what i know
- SID is the identifier of an Oracle Instance.
- An Oracle Instance is a group of programs and memory allocated for accessing the database.
- A database is a group of data files, control files etc.
- A database can be accessed by different instances at the same time.
- A instance can only access 1 database at a time.
From what i know, this are my questions below
1) An instance can only access 1 database(9i) at a time, but does that mean an instance can also access another database of different version(10g) at another time ? If it is possible, what parameter file should i look into ?
2) Can i run two or more instances in the same computer if each instance is assign to access different database of the same version or different version?
3) let say i have 2 instance each accessing a database of its own, how many listener do i need ?
4) when i look into tnsnames.ora, some of the connect_data contains SID, whereas some only contains service_name.
Can I know what is Service_Name ?
What is the difference between SID and service_name when use in accessing the database?
Any advices gurus? thanks deeply appreciated.
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| Re: Differences between Oracle SID / Instance/ Listener / Service or Service_Name / Database [message #302144 is a reply to message #302142] |
Sun, 24 February 2008 02:41  |
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Michel Cadot
Messages: 68718
Registered: March 2007
Location: Saint-Maur, France, https...
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Senior Member
Account Moderator |
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1) Before it is started, an instance is just a name. Depending on your ORACLE_HOME it can be associated to a version or another one, a database or another one.
2) Yes, with instance of different names
3) One, preferably (but not mandatory) of the latest version
4) Service_name is part of the SERVICE_NAMES parameter of your instance in init.ora or spfile.
They are 2 different ways to connect to the instance, see Database Net Services Reference, Chapter 6 Local Naming Parameters (tnsnames.ora), section Local Naming Parameters, subsection Connect Data Section.
Regards
Michel
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