At the moment we have 2 systems, and OS/PTF upgrades are applied to
the development/backup system first, then to the production system
once we're reasonably confident nothing went wrong. Soon we'll do
the same thing with live/development LPARs on a new system.
We wrote this into our SOX documentation and procedures, so we're
obligated to do this. Our auditors check from time to time.
Plus, it makes sense to test OS/PTF changes before we damage the
system the business relies on for success!
--Paul E Musselman