Database Software

Hi Experts,

Currently we have some changes on the rman retention policy from 168days to 90days.

RMAN Retention policy is:
CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 14 DAYS;

And RMAN Scripts monthly backup is:
run
{
allocate channel t1 type 'sbt_tape' parms
'ENV=(TDPO_OPTFILE=/opt/tivoli/tsm/client/oracle/bin64/tdpo_monthly.opt)';
backup as compressed backupset database tag ${SID}_MONTHLY keep until time 'sysdate+168';
release channel t1;
}

I believe I still have the old backup after I changed the 'sysdate+168' to 'sysdate+90'; on my scripts

How do I manage to delete this ?
Using, List backup and list backup summary will prompt me very long line and window,

How do I create the CONFIGURE settings I can remove the allocate channel... on my scripts ?

Cheers,
Raff