In addition to:

                BACKUP STGPOOL onsitetape offsitetape

I recommend you do:

                         BACKUP STGPOOL diskpool offsitetape

Because at any point in time, some of your backup data is in the disk
pool,
some in the tape pool.
This makes sure that if there is any data left in the disk pool that has
not
migrated to tape yet, it gets copied to the offsitepool.   (If there is
none
left in the diskpool, then the second BACKUP STGPOOL costs you
nothing...)

(In fact, you can save a WHOLE LOT of tape mounts if you do these in the
reverse order.
BACKUP STGPOOL diskpool offsitetape  FIRST; then your offsite tapes get
made
using only ONE tape mount for the output tape, instead of mounting INPUT
and
OUTPUT tapes. :>)

Here is something else you can do:

 select stgpool_name, sum(physical_mb)/1024 as physical_GB  from
occupancy
group by stgpool_name order by stgpool_name

This shows how many GB of data are in your disk and tape pool.

The sum of your diskpool and onsitetape pool should = the GB in your
offsite
tape pool.  It doesn't prove that EVERY file made it to the offsite
tapes,
but if this looks OK when I arrive in the morning, I'm happy..