> For some reason, the catalog does not seem to delete the entry.

Any error messages? Can you cut n paste the exercise? I do this all the time on 9i databases (target and catalog on 9i) and it seems to work fine.

> When I try doing some validation on the backup sets and archive log, RMAN is looking for some way older archives which no longer exists.

Again - please paste. It shouldn't be looking "way older" archives if you are connecting using the target controlfile (NOT the catalog) and your controlfile_record_keep_time=7.

> How to get rid of the old archive log information from the controlfile? ( present controlfile_record_keep_time is at default which is 7)?

See above. Are you using the catalog or the target controlfile?