To re-use a tape from a backup set that you no longer need, insert the tape, choose Configure in the Retrospect Directory, and click Devices. The Tape Devices window that appears shows you the name of the tape. Select the tape and choose Erase from the Devices menu. The next time Retrospect requests a new member for a backup set, it will automatically use this or any other erased tape in the backup device.

You should also remove the old backup set's catalog. Click Backup Sets from the Retrospect Directory's Configure tab. In the Backup Set selection window that appears, select the old backup set and choose Forget from the Backup Sets window. In the Finder, drag the old backup set catalog file to the Trash.