Re: Performance tuning suggestions

Tim,

In a message dated 98-02-18 01:03:18 EST, you write:

> I have been handed the chore of performance tuning an IBM F50 (192MG
>  mem) AS400 at release V3R2.  Any suggestions as to what would be a good
>  route for me to follow?  I previously changed the system value QPFRADJ
>  to be '2' which means the AS400 can optimize its pools at IPL and at
>  radic intervals throughout the day, yet there are some major system bog
>  downs still occurring.

(Sorry for the soapbox)

Spankedy, spank!  Yes, performance opinions are like (well, you know) and
others will probably disagree (although the latter seem to always have a
maxed-out system) _HOWEVER_, I _STRONGLY DISAGREE_ with setting any value for
QPFRADJ other than ZERO (zip, null, nada) for a 9406 system.  I've said it
before, and I'll say it again -- "automatic performance adjustment was
designed for 9402/4 systems, and always adjusts larger systems at
approximately the same time you no longer need memory in the pool that QPFRADJ
just sent it to".

As usual, there is no _one_ answer.  Assuming that you have already moved out
of QBASE, have you moved all heavily used subsystems into their own pools
(QCMN?)?  Have you monitored WRKSYSSTS during your "major system bog down"
intervals?  Have you set your activity levels high enough that INEL waits are
zero?  Have you moved memory around enough so that all subsystems are as close
to zero on faulting as they can be?  Have you checked WRKDSKSTS to ensure that
you haven't added DASD that is taking all the hits (if you add DASD, new disks
will get all the WRITE activity unless you perform a scratch restore following
install).

Beyond the above, you must read and _understand_ the "Work Management Guide"
for the AS/400 (yeah, I've said _that_ before, too).  Like my first mentor
said upon handing me almost 2K pages of OS, programming, and hardware manuals
18 years ago "Read this.  If you don't understand it, read it again.".  As
stated earlier, everyone has their own opinion about /400 performance tuning.
The latter is due, in large part, to the vast number of configuration options
available for the platform.  Depending upon their applications, smaller
systems can get away with setting QPFRADJ to 2 or 3.  Configurations involving
the IPCS and/or client/server require more study, regardless of size.

If the subsystems and memory have been optimized, follow the guidelines stated
here under another thread.  Ensure that you don't have too much activity on
any single disk unit.  If faulting under WRKSYSSTS is _still_ too high, you
need more memory.  If queries or SQL are eating too much CPU and you have
multiple processors (not likely on an F50), check out SMP.  If you're running
large-capacity drives and accessing data heavily, you may just need more disc
arms.  If all else fails, you might need a larger processor.

If, if, if.  As we say here in the South, "if a frog had wings, it wouldn't
bump its butt every time it hopped".  There are just _far_ too many variables
involved in performance tuning to even say "Hey, tell me whatcha' got and I'll
fix it" (and kill anyone _on the spot_ that says that they can ;-)).  The
"Work Management Guide" and a few intense sessions with WRKSYSSTS are your
best defense...

IMHO,

Dean Asmussen
Enterprise Systems Consulting, Inc.
Fuquay-Varina, NC  USA
E-Mail:  DAsmussen@aol.com

"Money doesn't always buy happiness.  People with ten million dollars are no
happier than those with nine million dollars." -- Hobart Brown
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