Actually, the dsmserv task is 400MB including the 256MB pool according to
topas.  If I add up all of the processes on the system I about 512MB.  This
means my maxperm should be at least down to 75 (percent).  I am planning to
knock it down to 70.

The place I seem to have taken a hit is on database backups now.  I am not
sure if fixing maxperm will help this or not.

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


-----Original Message-----
From: Tab Trepagnier [mailto:Tab.Trepagnier AT LAITRAM DOT COM]
Sent: Monday, September 16, 2002 6:48 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: Optimal VMTUNE Guidelines for a TSM Server


Paul,

You're close.  This is what I did.

Using your numbers, your process memory would be:
256 MB DB Buffer Pool
~ 128 MB for other processes (this is just a rule of thumb - not precise)
===== ~ 384 MB, so your 400 MB estimate is pretty good.

(2048 - 400) / (2048) = 80.5%

Thus the 80% maxperm is about right.  Understand how AIX uses VM.
* Only processes page to disk.
* "maxperm" determines how much memory is used for open file pages AND
cached file pages.

If a process needs another page for private memory or to access another page
of an open file, it will look for that memory page in this order:
- free RAM
- cached file pages, in which case the cached data is discarded.  File pages
with open file locks are not candidates, so AIX won't use them.
- process memory pages (this is what gets paged because the data and the
state of the page have to be saved).

Since the default "minfree" is 120 pages, there is a very high likelihood
that AIX will have to draw from the cache.  But that's OK - it does not
cause disk paging.

The key  performance ratio in that case is the count of pages "scanned"
divided by the count of pages "freed".  In other words, AIX looks through a
set of "candidate" memory pages looking for pages that it can reuse.  In
vmstat, those are the "sr" and "fr" columns respectively.

The AIX rule of thumb is sr/fr should be less than three; meaning AIX
shouldn't have to examine more than three candidate pages to find a usable
page.

I have an Oracle server where sr/fr is 1.1;  before I added memory to my TSM
server sr/fr was about 16.  In neither case was there significant disk
paging.

Good luck.

Tab Trepagnier
TSM Administrator
Laitram Corporation









"Seay, Paul" <seay_pd AT NAPTHEON DOT COM>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU> 09/16/2002 
05:00
PM Please respond to "ADSM: Dist Stor Manager"


        To:     ADSM-L AT VM.MARIST DOT EDU
        cc:
        Subject:        Optimal VMTUNE Guidelines for a TSM Server


I am trying to figure out what these are.  The defaults are not good on a
large server.

The suggestion is figure out how much memory does dsmserv need and then work
from there.

So lets take the example of a 2G server with a buffer pool of 256MB and an
overall memory requirement of 400MB.  That would make you think there is
about 1.6GB left around.  Problem is the default filesystem maxperm is 80%
of the 2GB or about 1.6GB.  This would mean nothing left for the rest of the
processes, thus lots of paging.  I am thinking a buffer of about 128MB
should be in there.  So, in this case, maybe set maxperm to 65%.

The real question is what other vmtune knobs should be considered in a TSM
server.  The IO prefetch, large or small?  Is there a book on how to do
this?

ETC
ETC.

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