>But the BACKUP DB to tape therefore need 2 tapes, because one contains the
>active version which can't be deleted. Therefore the BACKUP DB needs another
>tape if I want to BACKUP DB to tape.

Again, the Backup operation itself does *not* demand that there be 2 tapes.
It is the DELete VOLHistory command which wants at least one backup copy
to be existent.  See APARs IX86694 and IX86661.
You should not be trying to skimp on tapes in such matters: you cannot
afford to lose the *SM database.  If your management is on your case
about spending money on a few tapes, question them as to why they are
doing backups.
   Richard Sims, BU