DB_NAME, DB_UNIQUE_NAME, SERVICE_NAMES, INSTANCE_NAME, and $ORACLE_SID

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Relationships among DB_NAME, DB_UNIQUE_NAME, SERVICE_NAMES, INSTANCE_NAME, and $ORACLE_SID

Names Among MAA

Under Oracle Maximum Availability Architecture (MAA), we might be confused about various kinds of name. Here I try to clarify these names by chart and table.

DB_NAME (Enterprise-wide Name)

You must set this parameter for every instance in order to startup the database. If you didn't assign DB_NAME at installation-time, then

DB_NAME = $ORACLE_SID

DB_UNIQUE_NAME (Site-wide Name)

If you didn't assign DB_UNIQUE_NAME in the parameter file at startup-time, then

DB_UNIQUE_NAME = DB_NAME

If you didn't assign SERVICE_NAMES in the parameter file at startup-time, then

SERVICE_NAMES = DB_UNIQUE_NAME

INSTANCE_NAME (Server-wide Name)

If you didn't assign INSTANCE_NAME in the parameter file at startup-time, then

INSTANCE_NAME = $ORACLE_SID

Naming Scope and Default Values

Parameter NameName ScopeDefault ValueLevel
DB_NAMEEnterprise-wide= $ORACLE_SID
(Installation-time)
Database
DB_UNIQUE_NAMESite-wide= DB_NAME
(Startup-time)
Role
SERVICE_NAMESSite-wide (or Enterprise-wide)= DB_UNIQUE_NAME
(Startup-time)
Role (or Database)
INSTANCE_NAMEServer-wide= $ORACLE_SID
(Startup-time)
Instance
$ORACLE_SIDServer-wideN/AInstance

The above featured image illustrates you a hierarchy tree for better understanding on the relationship among names. For more details, you may check DB_NAME and DB_UNIQUE_NAME in Oracle documentation.

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