We do:
1) Backup Disk
2) Backup Tape
3) Backup DB
4) Run checkouts to get tapes off site.
5) Migrate
6) Expire
7) Backup DB
8) Run Checkin of scratch tapes to fill library (This could be done as part
of step 4 as well).

The first DB backup will be use for Disaster Recover of the server.  There
is no need to migrate data on onsite storage pools because you won't be
using the primary pools at a DR.  The second DB backup will be used if you
have to restore your DB because of corruption.  In this case it is best to
have the data migrated so you don't have to restore data to disk.

Kyle
payne AT berbee DOT com