Oracle Recovery Manager (RMAN) maintains a record of database files and backups for each database on which it performs operations. This metadata is called the RMAN repository. When you request recovery of a database, RMAN uses the repository metadata to choose the most efficient backups needed for this restore and recovery.
The primary location for the RMAN repository for a database is its control file. The importance of this metadata for RMAN is one more reason why protecting your control file is a vital part of your backup strategy. In some installations, a second copy of the RMAN repository is stored in a schema called the recovery catalog. The recovery catalog is located in a separate database and can store metadata for multiple target databases.
It is recommended that you use a recovery catalog. Because a recovery catalog stores metadata history for longer than the control file, you can perform a recovery that goes further back in time than the history in the control file. Also, if the target control file and all backups are lost, then the RMAN metadata in the recovery catalog can be used.
See Also:
For more information about creating and managing a recovery catalog, see Oracle Database Backup and Recovery User's Guide