RE: Memory Performance - When is RAM over committed ?

The problem is the faulting rates only have "guidelines" which can
sometimes be hard to communicate to management. A hard number can be
easier to communicate.

Try using SETOBJACC to see exactly what amount of memory is free in any
pool at the current time:

SETOBJACC OBJ(FILE) OBJTYPE(*FILE) POOL(*BASE)
or
SETOBJACC OBJ(FILE) OBJTYPE(*FILE) POOL(*SHRPOOL1)

Will return a message CPC1140: 189K of FILE brought to pool with
5509556K unused. The second number is the amount of free RAM in the
pool at the time. If that number is routinely zero or very small your
memory is overcommitted.

I've found that "real" numbers are much more persuasive than guidelines.

It would be fairly easy to put this into a batch program that ran at
regular time frames and create a memory usage chart similar to your CPU
usage charts. Remember that the performace adjuster will most likely be
changing the pool sizes continuously as well. Don't forget to purge the
object after you check the memory usage.


Regards,

Scott Ingvaldson
Senior IBM Support Specialist
Midwest Region Data Center
Fiserv.


-----Original Message-----
From: Graap, Kenneth [mailto:Kenneth.Graap@xxxxxxxxxxxxx]
Sent: Monday, July 20, 2009 10:44 AM
To: Midrange Systems Technical Discussion
Subject: Memory Performance - When is RAM over committed ?

Which performance measurement value(s) do you think would provide the
best evidence that memory (RAM) is beginning to be over committed on the
iSeries?

Do you think an analysis of faulting as a percentage of total disk
operations would provide a good objective measure of this, or would some
other measurement combination be better?

I would like to be able to provide objective evidence to upper
management that it is time to purchase additional memory... Even though
I know from experience that adding memory to the iSeries is ALWAYS a
good idea if throughput and/or response times start to increase...

Oh yes ... and please consider printing multiple copies of this e-mail
on green-bar paper.... <smile>

P
Please consider the environment before printing this email

Kenneth
Kenneth E. Graap
Systems Administrator
NW Natural
keg@xxxxxxxxxxxxx
503-226-4211 x5537