Either using with RMAN command "delete backup", or
during dropping database with "drop database including backups"
2. However, if we forget to follow above sequence, we still have manual way to achieve the same.
2.1 Manually delete backups from DISK, usually they should be under FRA.
2.2 Connect to catalog database without specifying target
rman rman/password@RCAT
> set dbid=
> unregister database;
e.g.
> rman catalog rman@RCAT
Recovery Manager: Release 11.2.0.3.0 - Production on Fri May 13 15:20:03 2016
Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.
recovery catalog database Password:
connected to recovery catalog database
RMAN> set dbid=649569281;
executing command: SET DBID
database name is "CTCG" and DBID is 649569281
RMAN> unregister database;
database name is "CTCG" and DBID is 649569281
Do you really want to unregister the database (enter YES or NO)? yes
database unregistered from the recovery catalog
RMAN> exit
