IDS Forum

RE: shared memory

Posted By: Marcus Haarmann
Date: Tuesday, 2 January 2007, at 7:36 a.m.

In Response To: RE: shared memory (Marcus Haarmann)

forwarded

-----Original Message-----
From: Gentry, Mark [mailto:mark.gentry@staples.com]
Sent: Tuesday, January 02, 2007 1:20 PM
To: 'Marcus Haarmann'
Subject: RE: shared memory [8074]

Try running "onstat -g mem" from time to time. Look for growing usage, like
"rsam" I've see this on my servers running 9.4 and believe it also occurred
at 7.x. If rmsam is growing, look for some new process that is not closing
CURSORS. If possible, compare the results with another instance.
"SHMTOTAL 0" means Informix will allocate as much memory as the kernel will
allow. Typically this is 2 gigs but only your SA knows for sure. Consult
with the SA to see how much physical memory is actually being used. You may
need to add more memory to the box and/or gen a new kernel allowing larger
memory segments.

-----Original Message-----
From: Marcus Haarmann [mailto:marcus.haarmann@midoco.de]
Sent: Tuesday, January 02, 2007 5:03 AM
To: ids@iiug.org
Subject: RE: shared memory [8074]

Hi,

Your shared memory is used because Informix needs it. It is that simple.
Shared memory is being allocated for each connection. I saw systems with
several Gb of Shared memory.
Why do you think the 100000 is a maximum value for initial segment ? What OS

is being used ?
The system settings (SHMMAX) have to be adjusted to have bigger segments,
but it is no problem to have an initial segment of e.g. 800 MB.
Update statistics takes itself a lot of shared memory, and onmode -F is only

working good if you have a total free segment.
In order to decrease shared memory, the only choice is to modify the
application, work with less users or decrease the buffer value.
It depends on your OS when Informix will not be able to allocate more
segments (SHMSEG parameter and some others), but if you have a relatively
constant amount of users/connections on your system, it will not allocate
more memory segments.

Marcus

-----Original Message-----
From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of S
SURESH
Sent: Tuesday, January 02, 2007 10:32 AM
To: ids@iiug.org
Subject: shared memory [8073]

In our IDS 7.31 server, onstat -g seg displays seven 'V's (Memory Segments).

SHMVIRTSIZE 100000
SHMADD 100000
SHMTOTAL 0

At present 6th "V" is in use and one is free. Each memory segment is quickly

getting exhausted.

Why its getting utilised very quickly
im running update statistics for entire db everyday Could this be the
problem.

Im not able to increase OS shmmax parameter its already maximum.
I believe after certain no of segments IDS will not add new segments.

Im using onmode -F, to release unused memory.but its releasing very less.

Is there a method to control the memory usage.
Please suggest forward path to solve this problem.

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Messages In This Thread

• shared memory
  S SURESH -- Tuesday, 2 January 2007, at 4:31 a.m.
  • RE: shared memory
    Marcus Haarmann -- Tuesday, 2 January 2007, at 5:02 a.m.
    • RE: shared memory
      Marcus Haarmann -- Tuesday, 2 January 2007, at 7:36 a.m.
      • RE: shared memory
        Dominic Seah Chin Teck -- Wednesday, 3 January 2007, at 12:17 a.m.

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