RE: Calculating Physical memory for Oracle Sessions

From: Jesse, Rich <Rich.Jesse_at_qg.com>
Date: Thu, 30 Nov 2006 13:13:18 -0600
Message-ID: <FB5D3CCFCECC2948B5DCF4CABDBE6697A52630@QTEX1.qg.com>

Jared, wouldn't your formula multiply shared memory (e.g. Oracle SGA size as reported by "ipcs -ma") by the number of Oracle processes (except for procs that don't connect to the instance, like the listener)? I think using ps output that way would be like saying that adding 25% of "X" and 25% of "Y" must equal 50% of "X+Y".

While I've never taken the time (had the time?) to dealve into it, I think that pmap is accurate iff shared memory is accounted for. The trick is to determine if any other process is accessing that shared memory. My knee jerk is that this could be accomplished by making a "master" list of shared memory (possibly using pmap outputs) to evaluate against whatever subset of processes you would want to see.

This blog item mentions this problem, but doesn't really offer a solution:

http://virtualthreads.blogspot.com/2006/02/understanding-memory-usage-on -linux.html

Kinda wierd that no one's thought of a solution (even if it's only a 99% one) to this, ain't it?

My $.02,
Rich

From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Jared Still Sent: Thursday, November 30, 2006 11:18 AM To: panandrao_at_gmail.com
Cc: tim_at_evdbt.com; ORACLE-L
Subject: Re: Calculating Physical memory for Oracle Sessions

On 11/29/06, Anand Rao <panandrao_at_gmail.com> wrote:

Tim,

There are lots of good AIX goodies for processes :)

From AIX 5.3, procmon is a great to use that gives you a more detailed and elaborate "pmap" like service.

procmon is a GUI tool (but surprising useful unlike many others).

Are they accurate?

It has the following options to perform detailed process analysis,

	procfiles
	..
	
	Of course, pmap is much easier to use as it is a single

command-line tool.

Here's why I asked about the AIX memory tools.

pmap is notoriously inaccurate. Memory accounting tools in Linux don't work too well. Try adding up all the memory reported by ps -fywluoracle | awk '{ mem=mem+$8 } END{ mem=mem*1024; print "bytes: ", mem}'
on a linux box, and it will be quite a bit more than actual do to double or triple counting of memory against RSS.

The same situation may exist on AIX, as it is my understanding that many

unix's suffer from this malady.

-- 
Jared Still
Certifiable Oracle DBA and Part Time Perl Evangelist


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Received on Thu Nov 30 2006 - 13:13:18 CST