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Oracle® Database Reference
12c Release 1 (12.1)

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Property Description
Parameter type String
Syntax COMMON_USER_PREFIX = prefix
Default value C##
Modifiable No
Basic No
Oracle RAC Multiple instances must have the same value

COMMON_USER_PREFIX specifies a prefix that the names of common users, roles, and profiles in a multitenant container database (CDB) must start with. Names of local users, roles, and profiles must not start with the same prefix. A case-insensitive comparison of the prefixes for user, role, and profile names to the value of this parameter is done.

By default, this parameter is set to C##.


Regardless of the value of the COMMON_USER_PREFIX parameter, the names of local users, roles, and profiles cannot start with C##.

If COMMON_USER_PREFIX is set to an empty string, Oracle will not enforce any restrictions on the names of common or local users, roles, and profiles.


Setting this parameter to an empty string will result in no restrictions being placed on names of common and local users, roles, and profiles, which could lead to conflicts between the names of local and common users, roles, and profiles when a PDB is plugged into a different CDB, or when opening a PDB that was closed when a common user was created.

When a value is set for COMMON_USER_PREFIX, Oracle will require that the names of common users, roles, and profiles start with the string assigned to this parameter.

The names of users, roles, and profiles created using this prefix must be valid names.


This initialization parameter is available starting with Oracle Database 12c Release 1 (

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