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Keyword: BASIS
Title : SAP on DB2 for Linux, UNIX and Windows: Important SAP Notes

Prerequisites

Procedure

By using the following parameters, you can limit the maximum use of the process-specific memory. This in turn limits the maximum use of swap space by an R/3 application server.

Consider the following parameters:

You can find more information on the functions of these parameters under Limits for Allocating Heap Memory in Functions of the R/3 Memory Management System.

Normally, only background work processes use a large amount of swap space.

Dialog processes do not usually use a lot of swap space, as long as the following conditions apply:

• The R/3 Extended Memory is not used up (set with parameter
em/initial_size_MB); and
• Not many of the user contexts have exceeded the upper limit for using the Extended Memory (set with parameter
ztta/roll_extension).

The following generally applies: The more main memory that an application server has, the better the performance.

If the CCMS Alert Monitor or Transaction ST06 (see Monitoring the Status of the R/3 System) displays a high paging rate for the operating system, decrease the size of the roll and paging buffers (only Windows NT and UNIX). In the profile management of the CCMS, set the profile parameters rdisp/ROLL_SHM and rdisp/PG_SHM to 0. You must change the profiles used by the R/3 application servers on the relevant host system.

If free memory is available even during heavy system usage, or if there is only low paging activity, you can increase the size of the roll and paging buffers. This decreases the accesses to the hard disk caused by rolling and paging.

The data segment size restricts the size of a user context that is executed as an R/3 background job. The default value is 64 MB, which is however, not sufficient and should be increased.

Set the data segment size for a process to the following values:

You can check data segment sizes using the R/3 test program memlimits. (You must stop the R/3 server to do this.) Note the output row that appears as follows: Process xxxxx allocating. The segment size is displayed in the row Size = .

For more detailed information, also refer to the R/3 installation guide in the section covering UNIX kernel parameters.

Prerequisites

Check if your host system fulfills the SAP recommendations regarding main memory and swap space.

Check the resources and system-specific requirements on all host systems on which an R/3 server is to be installed. For more information, see Checking the Hardware and Operating System of the Host System.

Procedure

Set the R/3 profile parameters that influence the memory management system.

Set these parameters in the instance profile that is used by the R/3 application servers in your system. For more information, see the CCMS Guide.

If you modify the profiles directly with a system editor, you must perform an error check. For more information, see Checking the Hardware and Operating System of the Host System.

The configuration of the memory management system depends largely on the number of users for each R/3 application server. Various configurations are described in the following units:

Application Server with Up to 15 Users

Application Server with Up to 50 Users

Application Server with Over 50 Users

You can find a general parameter overview for Windows NT under Parameter Overview for Windows NT.

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Keyword: BASIS
Title : UNIX Commnads for BASIS