ROOTVG

Dear All

I have added quite a lot of memory to a partition using dynamic allocation (went from 32Gb to 108Gb) on a P570 server and the partition is running AIX 5300-06-03-0732. Is there anything else that needs to be done (i.e. cfgmgr, etc.)

The customer is having shared memory errors in the SAP application and I want to ensure it's not to do with the DLPAR commands.

One thing you should do is insure the system sees all the new memory with prtconf and other commands like topas.

You will at some point want to verify other SAP performance tuning settings. You will need to sitdown with your SAP and/or Oracle support to determine what all your vmo settings should be, as well as AIO and other things.

Thanks for your reply.  ;D

Yep, no problems there, both the prtconf -m and lsattr -El mem0 showed all the memory available, both topas and nmon the same. The partition also had enough paging space to cope.

Luckily enough that has also been done already. We have all been (both app support and Sys Admins) surprised by the problem.

The server was rebooted to change the profile as the maximum was not enough to allow all the CPU's and memory required and the larger memory was dynamically allocated before the app started.

Well, my friend, the best advice I can give you is the obvious, if memory is all there, and there are no obvious ceilings (or floors) being hit that you can track:

Reasearch that error message with SAP and see what they reccomend. It could be one of many vmo settings that needs to be changed, call IBM and open a PMR with sysperf for tips if you like as well, but I think calling SAP would be my first choice.

Thanks for the reply, both are in hand. I'll await their responses. I just wanted to see if there was anything silly that may have come up with someone.

SAP should know what settings are needed on AIX to support these huge memory models. From the man page on shmget()
Technical Reference: Base Operating System and Extensions, Volume 2
shmget Subroutine

Purpose

Gets shared memory segments.
Library

Standard C Library (libc.a)
Syntax

#include <sys/shm.h>

int shmget (Key, Size, SharedMemoryFlag)
key_t  Key;
size_t  Size
int  SharedMemoryFlag;
Description

The shmget subroutine returns the shared memory identifier associated with the specified Key parameter.

The following limits apply to shared memory:

    * Maximum shared-memory segment size is:
          o 256M bytes before AIX 4.3.1
          o 2G bytes for AIX 4.3.1 through AIX 5.1
          o 64G bytes for 64-bit applications for AIX 5.1 and later
    * Minimum shared-memory segment size is 1 byte.
    * Maximum number of shared memory IDs is 4096 for operating system releases before AIX 4.3.2, 131072 for releases AIX 4.3.2 through AIX 5.2, and 1048576 for release AIX 5.3 and later.

In particular I am looking at this line:          o 64G bytes for 64-bit applications for AIX 5.1 and later. As you have 108G maybe the application is trying to utilize a shared memory segment > 64G. You may want to use svmon -P -t #N  or svmon -S -t #n to research the largest processes and associated segments, or simply the largest segments.

There are other options to svmon to easily see the pocess data you want to see: e.g. how many shared segments is the application trying to use, etc..