Check the value of Reusedelay parm in your tape storage pool(s). This
tells the TSM server how many days to wait after a tape becomes empty
before it is returned to the scratch pool for reuse. The default is 0 days,
the previous Administrator could have set it to another value and if that
much time hasn't elapsed since you deleted all of the filespaces and
backups, then your tapes won't have returned to scratch yet.

Rick