Catalog Backup

Hi,

1. I have catalog backup 2 copies with different retention.
15days in Disk and 1Month in Tape. is it fine?
or I should make it same retention?

2. I changed catalog backup in disk, from 1Month to 15days.
To free the space directly, how to delete the catalog backup data older than 15 days (note: I still have 1Month retention catalog backup in Tape)

Thanks,