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.
It stores much more extensive history of your backups than the control file due to limits on the number of control file records.
we can start the target database in the event of loss of controlfile using recovery catalog. Also The repository information is not saved in the controlfile when we make backup of control file.
Recovery catalog is a repository of metadata that is available in the control file of the target database. Whenver we take backups using RMAN the copy of the backup is placed in the control file in the form of reusable records and as well as in the recovery catalog in the form of tables. So that while taking recovery also these table info is useful to apply the backup data.
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