In Oracle Database 10gR1 Oracle introduced the RMAN command DROP DATABSE. This one simple statement has the ability to completely remove a database including all RMAN backups with the optional INCLUDING BACKUPS clause.
DROP DATABASE removes all data files, control files, online redo logs. The DROP DATABASE command can optionally delete backups including backup sets, proxy copies, image copies and archive redo logs from the target database from all configured device types.
If the target database is connected to a recovery catalog at the time DROP DATABASE is issued the target database will be unregistered as well as drop delete any backups known to catalog. If the command is issued in NOCATALOG mode then any backups known to the catalog will not be dropped but they will not be in the target database control file either.
The DROP DATABASE must be executed in RMAN while connected to the target database that is mounted and not open and started in RESTRICT SESSION.
Below is a demonstration of the DROP DATABASE command that will drop the database and all backups associated with the database. The Database in the example was not registered with a recovery catalog.