What the diff

[kummisara]

Iam a beginner in Oracle DBA just wanted to know the diff between
ORACLE_SID, INSTANCE_NAME and DATABASE_NAME?????






thnx
Kumaresan

[mivey4]

Iam a beginner in Oracle DBA just wanted to know the diff between
ORACLE_SID, INSTANCE_NAME and DATABASE_NAME?????






thnx
Kumaresan

Hi kummisara,

At first it may seem a bit confusing. I know it took me sometime to grasp the concept as I'm sure many others as well, but an Oracle instance is essentially and at its most basic level an Oracle database.

Think of the ORACLE_INSTANCE as being just another component of the database that defines the processes and shared memory used to access information in the database.

The instance consists of the user processes, the Oracle background processes, and the shared memory used by these processes.

Each database must also be uniquely identified by a corresponding SID. (System Identifier). The SID is used to identify and connect to each database on a network via the tnsnames.ora file where the SID is resolved by its corresponding service name.

So you may have more than 1 database on the same system with the same name but the SID has to be unique for each of them. (Like a primary key). Typically the ORACLE_SID and DATABASE_NAME are the same by default but they may be different.

The thing to remember is that the DATABASE_NAME and its corresponding ORACLE_SID are directly linked so there can only be 1 SID per database.

If you still find the concept a bit difficult to grasp. I am giving you this comparison: (Its a bit crude but it should help you grasp the differences)

ORACLE_INSTANCE --> Human
DATABASE_NAME ----> Your name (may also be your nickname?)
ORACLE_SID ----> Your social security number

Get it now? :-)

Read the glossary
http://download-west.oracle.com/docs/cd/B10501_01/win.920/a95491/glossary.htm#432410

Cheers!