In general, it's never safe to have an external agent back up a database,
because the data is typically in transit and partially in memory, and so
the database manager is the one which should be doing provisioning of its
data.  The only time that an external agent (mksysb, tar, etc.) could safely
back up any database is if the database manager is shut down.
Don't waste time and space trying to make the database fit into the root
volume group, as it would just be a false sense of security.
Instead, let ADSM back up its database and spend your time gaining familiarity
with restoral/recovery techniques.
     Richard Sims, Boston University OIT  (a former database systems guy)