The automatic tuner will modify the machine pool, but within the limits set
by the parameters set in the WRKSHRPOOL command. So you could set a
minimum/maximum there.
Consider the performance tuning tooling on IBM I with some thought about how
it affects SQL and the optimizer. If you are a heavy SQL user then using
the automatic tuning available might not be helpful and actually slow SQL
down. The reason is the SQL optimizer first looks at its environment. If it
has not changed, run the optimized query without doing any further work. If
it has changed, IE: memory pools, then optimize the query and run it. The
optimization may not be as good as before and you're spending time doing the
optimization. Well over half my customers with heavy SQL use the
performance tools to balance initially then turn it off so it will not force
SQL optimization to run at every turn. When you think about it, sometimes
the automatic system is not the best solution.
For environments where the majority of the data access is record level, then
the performance tools do a great job of balancing the system.
--
Jim Oberholtzer
Chief Technical Architect
Agile Technology Architects
-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Steinmetz, Paul
Sent: Tuesday, April 15, 2014 8:36 AM
To: 'Midrange Systems Technical Discussion'
Subject: RE: Recovering your system - QMCHPOOL
Rob,
Refresh my memory, but I thought machine pool was set by the system value,
QMCHPOOL.
Auto tune takes care of everything but the machine pool.
Paul
-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of rob@xxxxxxxxx
Sent: Tuesday, April 15, 2014 9:29 AM
To: Midrange Systems Technical Discussion
Subject: RE: Recovering your system - QMCHPOOL
If you have auto tuner going you probably do not need to adjust it. That
recommendation is from the manual "Recovering your system". It's a section
intended for someone who is restoring to a new hardware box, in dedicated
state, with no performance tuner running. As a recommended initial size.
It's also followed by this statement:
"For a more precise setting of the QMCHPOOL system value, see the Types of
memory pools information center topic."
Rob Berendt
--
IBM Certified System Administrator - IBM i 6.1 Group Dekko Dept 1600 Mail
to: 2505 Dekko Drive
Garrett, IN 46738
Ship to: Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com
From: "Steinmetz, Paul" <PSteinmetz@xxxxxxxxxx>
To: "'Midrange Systems Technical Discussion'"
<midrange-l@xxxxxxxxxxxx>
Date: 04/15/2014 09:01 AM
Subject: RE: Recovering your system - QMCHPOOL
Sent by: midrange-l-bounces@xxxxxxxxxxxx
Production LPAR is 196gb, machine pool is currently 22gb, 15% would be 29gb.
R&D LPAR is 40g, machine pool currently 2gb, 15% would be 6gb Upgrade
partition is 6gb, machine pool currently .5gb, 15% would .9gb
Should I consider adjusting the machine pools upward?
Not having any performance issues.
-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [
mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of rob@xxxxxxxxx
Sent: Tuesday, April 15, 2014 7:49 AM
To: Midrange Systems Technical Discussion
Subject: RE: Recovering your system - QMCHPOOL
Sue,
Thank you for looking up that information.
Since the minimum memory per partition is 256MB, then this:
As a general rule, if the main storage size is 64 MB or larger, change the
QMCHPOOL system value to be 15 percent of the main storage size. If the main
storage size is less than 64 MB, change the QMCHPOOL system value to be 20
percent of the main storage size.
should be changed to:
As a general rule change the QMCHPOOL system value to be 15 percent of the
main storage size.
In all editions of the "Recovering your system" manual, 7.1 and on?
The only caveat being that this would be a good time to review this general
recommendation since it's a bit dated.
Rob Berendt
midrange.com
