Also, to enhance on Erica's response - there IS an interface that will allow you to delete the last xx files on a volume within CA 1. CA 11 uses this interface for restart operations. For example, you have a job that creates 5 files on a tape and now need to "restart" that job at step 3 (creating file-3). Normally, you would not be allowed to recreate file-3 because files 4 and 5 already exist. With CA 11 however, you can restart the job at step-3 and CA 11 will interface to CA 1 so that files 3, 4 and 5 are all deleted and you can create a new file-3, 4 and 5 with the restarted job.
I only mention this because you had specifically asked about deleting the last file on a tape.
Russell Witt
CA 1 Architect