RE: Automatic Performance adjustment

Scott:

I imagine the only reason "the majority" favored manual is because the majority 
of those responding felt comfortable with manual tuning. Those who most use 
auto-tuning possibly don't feel comfortable offering an opinion.

Personally, since somewhere in version 3 of OS/400, I've never seen a 
production AS/400 that didn't run better on a day-to-day basis with auto-tuning 
active. There'd be no rational way anyone could manually tune a number of the 
systems I've worked with to get even decent results for more than an hour or so.

As far as I know, there's no good reason not to auto-tune most systems, 
especially if the system is configured to take advantage of it to begin with. 
This means that subsystems should be configured with appropriate subsystem 
pools, including private pools where needed, routing and pre-start job entries 
should direct work to appropriate subsystem pools (tuning is almost pointless 
otherwise), work is started in appropriate subsystems, sufficient memory for 
shifting as needed should be available, basic shared-pool settings are 
reasonable, etc.

And in a pinch, even if auto-tuning is active, you can still make manual 
changes in order to react to exceptional circumstances. That item alone is 
enough to suggest trying auto-tuning. By starting with an adjust at IPL and 
automatic, you can get an initial set of pool sizes and activity levels to 
begin baselining. Then switch to straight automatic once settings start to 
fluctuate within a range.

If you need specific adjustments at regular times that anticipate change and 
don't want to wait for auto-shifts -- end of day or start of day, e.g. -- then 
add job scheduler entries that cause major shifts, perhaps one or two or more 
CLRPOOL commands plus related CHGSHRPOOL commands.

In short, I seldom have QPFRADJ at anything but 3 and I have no problem 
augmenting it with manual action. I don't see it as either/or nor as 
better/worse. Use both.

Tom Liotta

midrange-l-request@xxxxxxxxxxxx wrote:

>   4. Automatic Performance adjustment (Ingvaldson, Scott)
>
>I was curious about the Performance Survey last week.  I got the impression
>that the majority favored manual tuning of the system vs. automatic
>performance adjustment via QPFRADJ.  Personally, I have been a fan of
>QPFRADJ ever since it began using less than 1% of the CPU.
>
>1.)  What can I do to manually tune the system, that QPFRADJ cannot do
>automagically?
>
>2.)  Why would I want to spend time manually tuning the system when I can
>set up the basics and let QPFRADJ take care of the day to day(or hour to
>hour) fluctuations?
>
>Or does the majority favor setting QPFRADJ to 2 or 3?

-- 
-- 
Tom Liotta
The PowerTech Group, Inc.
19426 68th Avenue South
Kent, WA 98032
Phone  253-872-7788 x313
Fax    253-872-7904
http://www.powertechgroup.com


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