| 2.
Change
Control (continued)
The fact that you want
to test before you install in production does not mean that you have to
have to have an elaborate test infrastructure. You probably want to
maintain a spare computer for on the fly replacement due to critical
hardware problems anyway. What’s important is that when you test
software upgrades you adhere to some basic principals:
1.
Don’t
apply the change to critical live systems. You want to make a backup copy
of any data that will be or might be touched by the upgrade and test the
change on the backup copy first.
2.
Always back
up your production data and make sure the backup is usable before applying
changes to know you can back out the change if things don’t work despite
prior testing.
3.
Work out
the installation procedure in a non-production environment before touching
production equipment. This doesn’t have to be a separate network. Most
of the time a logically separate installation on the production hardware
can do the trick.
4.
Write out
the test procedures and the expected results and keep notes during the
tests.
5.
Never run
tests on production hardware during peek production times. Never apply
changes to central or critical production systems during regular
production hours.
6.
Schedule
down-time for the upgrade to allow sufficient time to solve potential
problems.
7.
Have a
back-out plan to reverse the change and restore the pre-change
functionality if necessary.
You
also want to set (limit) the scope of changes to an achievable target. For
example, when you apply multiple changes to a production environment, you
want to apply a single change to all computers before moving on to the
next one. This prevents you from running out of time while making several
changes to each computer at once and ending up with only a subset of the
computers updated. You can terminate the upgrade at a specific point and
continue during the next down-time window where you left off. Meanwhile
you’ve ensured continuous usability of the environment.
In
short: Have a plan! You want to know
Change control will be the most valuable tool for the System
Administrator to guarantee success. However, it can only work if you are
willing to trade out the freedom to let users have individual hardware and
software configurations.
(read
on ...)
Copyright (c) 2008 by In Scope-Solutions,
Inc.
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