Seay, Paul wrote:

Paging is a bad thing, but why would an AIX system page (like crazy) under
this configuration?

P660-6H1 2GB Memory
dsmserv using 384MB
Swap space is 3GB an only 12% used.
Nothing else seems to use much memory based on a ps -efl

An old MVS person like myself would say somehow something has a free page
target that is really high.  iostat and vmstat seem OK.

Any AIX gurus know the answer?

Paul D. Seay, Jr.
Technical Specialist
Naptheon Inc.
757-688-8180

Without seeing anything else, I'd have to say it looks like your maxperm
setting is too high. Do you have your databases on filesystems artehr
than raw logical volumes?

AIX uses spare memory for caching filesystem information. The paging
process is the same as that used for file IO (i.e. the VMM). If the
system is doing lots of fileIO, then active processes can be paged out
and that memory used for file buffers. This is (Almost always) a bad thing.

The amount of memory that can be used for file buffers is controlled by
several settings, the most important one is maxperm. That governs the
maximum amount of physical memory that can be used by the system for
file buffers. The default is 80%. Calculate what amount of memory you
require for the processes that run, and drop maxperm down till you no
longer have to page.

To change maxperm, use the vmtune command

/usr/samples/kernel/vmtune -P <percentage>

WARNING!

Because vmtune changes the running kernel, run it first with NO
parameters to check that you get valid numbers. If someone has put a
copy of vmtune on the system (WIthout installing it properly. i.e.
copied it from another system) it can get out of sync with the kernel,
and the system will crash if you attempt to change the values. (If it's
wrong, most of them come up as -1).

Hamish.


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