Well,
It seems you have a problem then.
db2adutl, the supported way to expire DB2 backups use just the time as a criteria to delete backups.
Try this:
1. db2adutl query
Save the output
2.db2 update db cfg for sample using TSM_MGMTCLASS MONTHLY
db2adutl query
Compare output from 1 to output from 2. I think they will be the same, but I am not sure. If they are the same this option will not work.
The other option is to get a list of the timestamp for each backup according to the mcclass (using db2adutl query). And them delete selectively using
db2adutl delete full taken at <timestamp>
You can write a script to parse this.
Hope this helps,
Rudy
Edit: I just realized that srikumar_1 has already suggested that in his post above.