DBNEWID Utility

DBNEWID is a database utility that can change the internal, unique database identifier (DBID) and the database name (DBNAME) for an operational database. The DBNEWID utility lets you change any of the following:

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Only the DBID of a database
Only the DBNAME of a database
Both the DBNAME and DBID of a database
Therefore, you can manually create a copy of a database and give it a new DBNAME and DBID by re-creating the control file, and you can register a seed database and a manually copied database together in the same RMAN repository.