Oracle Database Discussions

I have this problem for the past 2 weeks.
I can't delete the old backup files in RMAN. I do crosscheck backup, and crosscheck backupset. all the files are marked available.
If I choose to crosscheck backupset 1125, 1126. it will check them as expired, and I can delete. Otherwise, when I do
delete obsolete
it shows me,
RMAN retention policy is set to redundancy 1
no obsolete backups found

I have about 10 dates of backup. I can delete them manually, but that is not quite what I want. I want them to be deleted when i am doing my rman backup.
Thank you very much.
Here is my rman per script:

$rman_script="backup device type disk filesperset = 1 tag '%TAG' database;
backup device type disk filesperset = 1 tag '%TAG' archivelog all delete all input;
allocate channel for maintenance type disk;
crosscheck backupset;
delete noprompt obsolete device type disk;
release channel;
";
$result = backup();
exit($result);

thanks.