RMAN always stores its latest backup operations in the target database control file. You can set up an optional recovery catalog to store metadata regarding RMAN backups. The recovery catalog is a separate schema (usually in a database different from that of the target database) that contains database objects (tables, indexes, and so on) that store the RMAN backup information. The recovery catalog doesn’t store RMAN backup pieces—only backup metadata.
The main advantages of using a recovery catalog are as follows:
- Provides a secondary repository for RMAN metadata. If you lose all your control files and backups of your control files, you can still retrieve RMAN metadata from the recovery catalog.
- Stores RMAN metadata for a much longer period than is possible when you just use a control file for the repository.
- Offers access to all RMAN features. Some restore and recovery features are simpler when using a recovery catalog.
The disadvantage of using a recovery catalog is that this is another database you have to set up, maintain, and back up. Additionally, when you start a backup and attempt to connect to the recovery catalog, if the recovery catalog isn’t available for any reason (server down, network issues, and so on), you must decide whether you want to continue with the backup without a recovery catalog.
You must also be aware of versioning aspects when using a recovery catalog. You need to make sure the version of the database you use to store the recovery catalog is compatible with the version of the target database. When you upgrade a target database, be sure the recovery catalog is upgraded (if necessary).
RMAN works fine with or without a recovery catalog. For several of the databases I maintain, I don’t use a recovery catalog; this eliminates having to set it up and maintain it. For me, simplicity takes precedence over the features available with the recovery catalog.
However, if you have good business reasons for using a recovery catalog, then implement and use one. The recovery catalog isn’t that difficult to set up and maintain, and Oracle recommends that you use it.