If you're on a Unix box, doubtful because it doesn't appear many ADSM'ers
are, you can create a macro to update the storage pool and change your hi
and lo migration levels.  Run this macro in a cron job.  Use two of these,
one in the morning to lower the high water mark and one in the evening to
raise the high  water mark back.  Of course if you run out of optical disk
during the night's backups you'll have to migrate data to tape anyway.
We intend to run in this mode when we move to production backups on ADSM.
Our daytime levels will be hi=1 lo=0, at night they will be restored to
normal.  This will force all the previous nights data to tape (or the next
storage pool) freeing up the initial pool for the upcoming night.

   However if you're on MVS you're on your own.

Rich Campbell
Texas Instruments
richc AT ti DOT com