Yes, that is exactly what I want.
Sorry for being short.
I have six different pools and I do NOT want to distribute new tapes to the pools after inserting them into the library. Instead I want to leave them in the "free" pool and have them assigned automatically from there when a tape is needed. This works so far.
If a tape is needed VBR always takes a NEW tape. This is by design, I assume. So, as time goes by, there are no more tapes in the "free" pool.
This leads to the situation that - as long as there are tapes in the "free" pool - , the old and expired tapes remain in their pools, but are not used any further.
Once a pool needs a new tape, but has no expired ones, the job cannot continue, because there are no more tapes in the "free" pool and because it cannot take one the expired tapes of any other pool.