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Symptom

Corrective action

Help: These symptoms can occur if the maximum number of 10 shared memory descriptors is exceeded. You can find more detailed information under Shared Memory IDs under IBM AIX or in the OSS system in Note 28992.

In the operating system OSF/1 from Digital Equipment Corporation, you must increase the value of the parameter VPAGEMAX for the Extended Memory by up to 800 MB (parameter em/initial_size_MB = 800) to 131072. You can find more information on larger memory amounts in the OSS Note 32915 in the OSS system.

VPAGEMAX defines the size of the unnamed mapped file for the R/3 Extended Memory.

1) Goto transaction SE16
2) Enter the table name : agr_define
3) Enter the master role in the second role field ( this field is in the second row) and execute
4) Then you will see the derived roles based on the master roles

A shared memory ID is used for each shared memory segment (256 MB) used in a work process. There is a maximum of 10 shared memory IDs for each process. If the parameter em/initial_size_MB is set to a value up to 256 MB, an ID is used. However, if the value for this parameter is set between 256 and 512 MB, 2 IDs are used, and so on.

You must reduce the number of R/3 shared memory areas so that the memory management system can be used under AIX. This includes the areas in pools. For this, set the parameters ipc/shm_psize_ in the R/3 system profile.

Recommended pools:

• To shift the R/3 shared memory area 6 into the R/3 shared memory pool 10, use the following parameter settings:

ipc/shm_psize_06 =-10
ipc/shm_psize_10 =

• If the shift from area 6 is insufficient, shift area 41 to 49 into pool 10. Shared memory pool 4 is no longer required.

ipc/shm_psize_41 =-10
...
ipc/shm_psize_49 =-10...
ipc/shm_psize_10 =

The following are rules for memory management under Windows NT:

Minimizing the Windows NT File Cache

Maximum Use of Extended Memory

Setting Dimensions for Sufficient Extended Memory

Determining the Number of Work Processes, compared to reducing UNIX

Parameter Overview for Windows NT

• The Windows NT file cache directly competes with R/3 programs and pushes these programs out of the working memory. Unlike UNIX, the file cache is only indirectly influenced by a switch in the network setting.
• Writing and reading R/3 roll and paging blocks in the relevant storage files extends the Windows NT file cache and pushes out the R/3 programs from the working memory.
• Copying roll and paging blocks when changing contexts is more time-consuming than including memory blocks when using Extended Memory. Extended Memory also has the advantage that it is subject to the performance-oriented Windows NT paging mechanism.
• Windows NT does not offer you code sharing (exception: DLLs). This means that all work processes fill the complete memory area in the memory. This leads to a greater memory requirement for the work processes compared to UNIX.
• Pages in the Extended Memory that are not in the address area of an active process are transferred automatically in the page file by the operating system. The pages remain duplicated in the physical memory until the memory area is required by another process. They are marked as transferred. The transfer has a low priority and is described as a lazy page out. If a work process now accesses a lazy page out, the memory area is included again without the page file access. If there is enough working memory, the result is a large [page out] and a small [page in] value. When a lazy page out action occurs, Windows NT creates permanently free available working memory. Therefore, even a page-in with a page file access is faster than on UNIX systems, since it is not necessary to transfer another page beforehand (no direct page-out before a page-in).

The previous valid recommendations for setting the memory management cannot be completely used for Windows NT. The operating system can use other memory administration mechanisms than the various UNIX derivatives. You must evaluate the performance statistics displayed by transactions ST02 and ST06 (monitoring system performance) differently than with UNIX systems due to the above-mentioned reason.

This unit serves as a guide for setting the SAP R/3 Memory Management under Windows NT. By using this guide, the system administrator for a Windows NT application server should be better able to evaluate the performance of the system and to tune the system accordingly.

Implementing the memory management system under Windows NT is described in Implementation on Windows NT.

To find the guidelines to configure the memory management under Windows NT, refer to Rules for Memory Management under Windows NT, and for a quick overview of all important parameters, refer to Parameter Overview for Windows NT.