From what I can tell, IBM has resolved most of the CPU/storage creeps
that caused the increase in CPU time as time elapses from the last
IPL. Of course, new problems could crop up, but in general, you
shouldn't need to IPL more often than every three months. The
difference in JOB times used to be measurable, but it's getting much
harder these days. The variability of job CPU times run the same day
is much higher on the z10s than you would be able to measure when
analyzing job CPU times from three or six months apart.
If it were my installation, I would tend to follow IBM's
recommendations, which are to install the latest RSU once a quarter
(which almost always requires an IPL - I think). Then weekly assess
any HIPER or PE PTFs to estimate the applicability and risk to the
system. Apply them if you think the risk is high. This might require
an IPL. Obviously, you would want to test these on your test system
before applying them to production.
From a performance analyst's point of view, if I had a constrained
system, I would also review any New Function APARs. These often
provide very significant performance improvements.
And from a charge back or capacity planner's point of view, I would
also review all PTFs relating to SMF or RMF changes. It would be
frustrating to find out that a data field that you use for reporting
has been wrong for the last year.
And I strongly believe that a parallel sysplex environment that leaves
the applications available to users 100% of the time is the best
solution. Once you implement such a configuration, it doesn't require
you to keep any given LPAR up for several months at a time.
Although it's been mentioned in another thread, I think that Greg
Daynes and Brian Peterson's SHARE presentation on IBM's and a User's
maintenance recommendations is worthy of note here - http://ew.share.org/proceedingmod/abstract.cfm?abstract_id=20107
.
Best regards,
Cheryl
****************************
Cheryl Watson
Watson & Walker, Inc.
www.watsonwalker.com
****************************
On Sep 3, 2009, at 1:57 AM, Ron Hawkins wrote:
Tommy,
The only problem I'm aware is that there may be an increase in CPU
time for
most programs and transactions the longer your system is up. I think
this
was first suggested by Cheryl Watson after a study back in the late
90s, and
I confirmed that it was happening using SMF from an LPAR that had been
up
and running for a few months (six months I think). I do not remember how
much increase there was.
I did hit an issue recently where I was purposely failing Storage
Controllers and IO Drivers to the controller would just hang and need
to be
cancelled or forced off the system. After several week of this testing
the
CPU utilization of the LPAR had more than doubled while generating the
same
IO rate. We scheduled an IPL and everything was back to normal.
It may worth choosing some sample workloads that run at all times of
the day
and track those over time to see if you are encountering any of these
affects to the point that it is pushing your MSU charges up.
Ron
-----Original Message-----
From: IBM Mainframe Discussion List [mailto:[email protected]] On
Behalf Of
Tommy Tsui
Sent: Wednesday, September 02, 2009 6:09 PM
To: [email protected]
Subject: [IBM-MAIN] How often IPL a production LPAR (any good
practice)
Hi all,
Is there any concern if we didn't IPL a LPAR over three months. Is
there
any good practise to follow from IBM. They always replied LPAR never
needs
IPL because of 24 x 7.
Any comment will be appreciated
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