Here's another twist on the problem.

We used ADSM and the SAP backint agent to back up our NT systems and
our SAP Oracle databases.  There were three "systems" which meant we
had six nodes (one for each NT system and one for each SAP system
running on them).  I kept the development and test systems
uncollocated and allowed them just to fill up the next available tape
space (four nodes sharing a tape storage pool) but I was careful to
use collocation for my production environment.

This gave me two separate copies of each day's backup of the online
redo logs for the database which was beneficial for disaster recover
planning.  Normally one would exclude the redo log directory from the
system level backup and allow the SAP backint agent to manage that
but, by including it in a collocated structure, I got one copy written
to tape as a "standard" file system backup and another copy written to
a separate tape during the backint backup.

Murray Nicholas
IT Systems Consultant
Galeforce Information Services Pty Ltd
email:  murray AT galeforce.bu.aust DOT com