A media manager is required for RMAN to back up directly to tape. Several vendors provide this feature (for a cost). Media managers are used in large Oracle database environments, such as data warehouses, in which you may not have enough room to back up a database to disk. You may also have a disaster recovery requirement to back up directly to tape.
If you have such requirements, then you should purchase a media management package and implement it. If you don’t need to back up directly to tape, there’s no need to implement a media manager. RMAN works fine backing up directly to disk.
Keep in mind that many shops use RMAN to back up directly to disk and then have the system administrator back up the RMAN backups to tape afterward. If you do this, you have to be sure your RMAN backups aren’t running while the tape backups are running (because you may get partial files backed up to tape).
