Configuration for AIX 

Prerequisites

Particular functions of AIX (late swap, allocation, disclaim) enable an alternative implementation of the extended memory with a size of several GB as of R/3 Release 3.1G kernel. A single user context can still only use approximately 1 GB of extended memory, but the sum of usable extended memory for all user contexts combined can be much higher.

Since a lot of extended memory is provided, you can set a high limit for the shared memory consumption. It is also no longer necessary to assign mainly heap memory in background processes to keep the usage of the extended memory low. Heap is particularly small on AIX.

You can also minimize roll memory, which accelerates the context switch (roll-in/out) and the dialog and background processing, for example, with synchronous updating.

This is described in more detail in the R/3 note 95454.

Procedure

Recommended parameters in the instance profile:

Parameter

Recommendation:

Meaning

ES/TABLE

SHM_SEGS

Switches to the alternative implementation of the extended memory (EM)

em/max_size_MB

4096

Enables maximum 4 GB of extended memory; can be larger if needed

ztta/roll_extension

500000000

Limit of approximately 500 MB (2 shared segments) of extended memory per user context

ztta/roll_area

3000000

Reduces consumption of roll memory in background processes

ztta/roll_first

1

Reduces consumption of roll memory in dialog processes

abap/heap_area_nondia

20000000 (20 MB)

Can be set relatively low, so that a heap bottle neck is avoided in the data segment

The following parameters should only be changed after consulting with SAP.

Parameter

Default

Meaning

es/shm_proc_seg_count

3

Specifies the number of shared memory segments that are used as shared and privately.

es/shm_max_priv_segs

2

This parameter must be lower by 1 than es/shm_proc_seg_count.

(=>2*256 MB is usable)

es/shm_user_count

1024

This describes the maximum number of users in all open sessions.

es/shm_user_count

 

This specifies the maximum number of AIX system segments that ESSHM uses.

See also: Shared Memory ID under IBM AIX

These recommendations depend not only on whether the alternative method of implementing extended memory is active, but also on the AIX version used.

The following R/3 notes relate to memory management under AIX:

Note Number

Short text

28992

AIX Number of shared memories exceeds 10

33576

Memory management in releases as of 3.0C, UNIX and NT

36410

AIX Early versus late swap space allocation

78498

High paging rate on AIX 4.x database servers

95454

Large amount of extended memory on AIX

124555

AIX Recommendation for maximum extended memory

132748

AIX ES SHM_SEGS error handling corrected

143646

AIX patches for new memory management (95454)

115220

Signal 11 and signal 4 on AIX