RE: Using OS/400 AutoTuner

Ken,

If you have Performance Tools, run some of the performance reports and look  at 
the exceptions analysis.  Also, you may want to create a BEST/1 model from some 
collected data and then play with the model.  You can reallocate the memory 
pools and see predicted results, although predictions and the real world have a 
habit of being different.   But, it's one way to play without 'hurting' your 
production environment.  You can then try making the changes for real and 
measure the results.  Your 'slowdowns' may have nothing to do with memory or 
disk, perhaps record locking, or comm waits, or .....

Glenn

-----Original Message-----
From: Graap, Ken [mailto:keg@exchange.gasco.com]
Sent: Monday, May 22, 2000 11:34 AM
To: 'Midrange'
Subject: Using OS/400 AutoTuner


We have one system supporting, production and development.

It is difficult to determine what kind of work will be submitted or run
interactively at any particular time.

In order to insure optimum memory allocation between storage pools, I am
using the OS/400 AutoTuner (QPFRADJ=3).

We have 16GB of RAM on our Model 730 and are at V4R4.

During the day I see as high as 10GB memory allocations between pools,
usually *Shrpool1 AND *Interact...

The pools are defined as follows:

                                                                 
              Defined    Max   Allocated   Pool  -Paging Option--
Pool         Size (M)  Active  Size (M)     ID   Defined  Current

*MACHINE       895.17   +++++      895.17    1   *FIXED   *FIXED 
*BASE         1638.40      72     1638.40    2   *CALC    *CALC  
*INTERACT     7807.52      30     7807.52    4   *CALC    *CALC  
*SPOOL          81.91      15       81.91    5   *FIXED   *FIXED 
*SHRPOOL1     5960.98      15     5960.98    3   *CALC    *CALC  

Batch work runs in SHRPOOL1.

I'm currently trying to figure out why we are experiencing periodic system
slowdowns even though our CPU utilization averages less than 20%, disk arm
utilization around 5% and faulting around 10-20 per second in *INTERACT and
*SHRPOOL, most of that being DB Faulting.

I'm able to control the memory allocation swings somewhat using the
WRKSHRPOOL command interface:

                       -----Size %-----  -----Faults/Second------ 
 Pool        Priority  Minimum  Maximum  Minimum  Thread  Maximum 
 *MACHINE         1      5.48      100     4.00     .00     6.00  
 *BASE            2     10.00    85.00    10.00    2.00      100  
 *INTERACT        2     25.00    85.00     5.00     .50      200  
 *SPOOL           4       .50     3.00     5.00    1.00      100  
 *SHRPOOL1        3     10.00    85.00    10.00    2.00      100  

I change the Minimum values to control how much storage is available to
reallocate....

I would prefer not to restrict memory allocation too much, because it can
result in substantial amounts of memory being left in a pool that isn't
being used. I would like to give the OS/400 tuning algorithm as much control
as possible over tuning, as long as it doesn't prove to be detrimental to
interactive response times or batch throughput.

I would suspect that large (10GB or more) memory reallocation might result
in some slowdown for interactive users as pages originally resident in RAM
are being written to disk, but could this be causing my system to slow down
significantly?

Any thoughts or comments are welcome. I'm just exploring possibilities...


Kenneth

****************************************
Kenneth E. Graap
IBM Certified Specialist
AS/400 Professional
Network Administrator
NW Natural (Gas Services)
keg@nwnatural.com
Phone: 503-226-4211 x5537
FAX:    603-849-0591
****************************************


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