RMAN delete obsolte backups

Hi,

I am using 11.2.0.3.0 , 2 node RAC datatabase on Exadata with ASM

I have  changed recovery window of 35 days to 14 days.

Now I am trying to delete old backup & backups sets older than 14 days, But I am getting errors.

RMAN> ALLOCATE CHANNEL FOR MAINTENANCE DEVICE TYPE DISK;

using target database control file instead of recovery catalog
allocated channel: ORA_MAINT_DISK_1
channel ORA_MAINT_DISK_1: SID=1381 instance=PCAPF31 device type=DISK

RMAN> delete obsolete;

RMAN retention policy will be applied to the command
RMAN retention policy is set to recovery window of 14 days
Deleting the following obsolete backups and copies:









  Backup Piece  
19420  05-MAY-14     
c-4245685800-20140505-03



RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of delete command at 05/20/2014 17:22:14
RMAN-06091: no channel allocated for maintenance (of an appropriate type)








===============================================
RMAN-03002: failure of delete command at 05/20/2014 17:22:14

RMAN> release channel;

released channel: ORA_MAINT_DISK_1


RMAN-06091: no channel allocated for maintenance (of an appropriate type