Why need to use RMAN a Recovery Catalog in oracle database 10g ?
RMAN maintains metadata about the target database and its backup and recovery operations in the RMAN repository. Among other things, RMAN stores information about its own configuration settings, the target database schema, archived redo logs, and all backup files on disk or tape. RMAN's LIST, REPORT, and SHOW commands display RMAN repository information.
The primary store for RMAN repository data is always the control file of the target database. The CONTROL_FILE_RECORD_KEEP_TIME initialization parameter controls how long backup records are kept in the control file before those records are re-used to hold information about more recent backups.
Another copy of the RMAN repository data can also be saved in the recovery catalog.
Using a recovery catalog preserves RMAN repository information if the control file is lost, making it much easier to restore and recover following the loss of the control file. (A backup control file may not contain complete information about recent available backups.) The recovery catalog can also store a much more extensive history of your backups than the control file, due to limits on the number of control file records.
In addition to RMAN repository records, the recovery catalog can also hold RMAN stored scripts, sequences of RMAN commands for common backup tasks. Centralized storage of scripts in recovery catalog can be more convenient than working with command files.
Except for stored scripts, all of RMAN's features work equally well with or without a recovery catalog.