Delete obsolete backups with RMAN in Oracle 11g

The RMAN retention policy specifies how many copies of backup we need to retain, By default, the value is 1.
Setting this parameter to 2 ensures that the latest two copies of datafile or tablespace backups is retained.

Check the retention policy of database

RMAN> show retention policy;

using target database control file instead of recovery catalog
RMAN configuration parameters for database with db_unique_name TESTDB are:
CONFIGURE RETENTION POLICY TO REDUNDANCY 1; # default

Take the backup of tablespace or database twice. In this case we will take tablespace backup

RMAN> backup tablespace users;

Starting backup at 22-OCT-15
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=41 device type=DISK
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00004 name=+DATA/testdb/datafile/users.259.892594189
channel ORA_DISK_1: starting piece 1 at 22-OCT-15
channel ORA_DISK_1: finished piece 1 at 22-OCT-15
piece handle=/u01/app/backup/TESTDB_69_%1.bak tag=TAG20151022T230309 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:07
Finished backup at 22-OCT-15

RMAN> backup tablespace users;

Starting backup at 22-OCT-15
using channel ORA_DISK_1
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00004 name=+DATA/testdb/datafile/users.259.892594189
channel ORA_DISK_1: starting piece 1 at 22-OCT-15
channel ORA_DISK_1: finished piece 1 at 22-OCT-15
piece handle=/u01/app/backup/TESTDB_70_%1.bak tag=TAG20151022T230337 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:03
Finished backup at 22-OCT-15

Check whether we have obsolete backups

RMAN> report obsolete;

RMAN retention policy will be applied to the command
RMAN retention policy is set to redundancy 1
Report of obsolete backups and copies
Type                 Key    Completion Time    Filename/Handle
-------------------- ------ ------------------ --------------------
Backup Set           67     22-OCT-15        
  Backup Piece       67     22-OCT-15          /u01/app/backup/TESTDB_69_%1.bak

Delete the backup that does not satisfy retention policy:-

RMAN> delete noprompt obsolete;

RMAN retention policy will be applied to the command
RMAN retention policy is set to redundancy 1
using channel ORA_DISK_1
Deleting the following obsolete backups and copies:
Type                 Key    Completion Time    Filename/Handle
-------------------- ------ ------------------ --------------------
Backup Set           67     22-OCT-15        
  Backup Piece       67     22-OCT-15          /u01/app/backup/TESTDB_69_%1.bak
deleted backup piece
backup piece handle=/u01/app/backup/TESTDB_69_%1.bak RECID=67 STAMP=893804592
Deleted 1 objects


RMAN>