>     I'm curious why you want ADSM halted before a reboot?

Assure database integrity.
Dismount any mounted tapes so that when ADSM comes back it
  won't think they're missing.

For a graceful shutdown, doing just a 'halt' may be too abrupt.
Ideally, when time permits, it would be good to be able to
disable new sessions, give some time for any to complete, then
cancel any remaining and Dismount Volumes for any tapes still
mounted.          Richard Sims, Boston University