Difference between oracle_sid and instance_name

Oracle_sid:

1, Used to mark system processes

2, Oracle_sidThe parameter is an operating system environment variable used to interact with the operating system. This parameter correspondsOracle_base,ORACLE_HOMESame usage

3, Oracle_sidSpecifies the name of the database parameter file.

$ Oracle_base/admin/db_name/pfile/init $ oracle_sid.ora

$ Oracle_base/admin/db_name/pfile/spfile $ oracle_sid.ora

4,

Instance_name:

1, Indicates a database instance.

2, The database instance name is used for external connection with the operating system.OracleListener(Listener)In the configuration fileSid_nameIs fromInstance_nameThe relationship between database names and instance names is generally a one-to-one correspondence. A database name has an Instance name. If you create two databases on a server, there are two database names, two database instance names are used to identify a database. The user and instance are connected.

OS <----------------> OracleDatabase<-------- (Instance_name (Instance name))

instance_name and oracle_sid is the same by default. In fact, oracle_sid and instance_name it does not matter. oracle_sid , when the external connection is used for database interaction, instance_name is used. When multiple databases are installed on the same server, the operating system uses oracle_sid to differentiate processes of different instances, when we connect to different databases on this server, instance_name is used to determine the database to be linked.