ztta/roll_extension: Extended Memory Limit

Use

The value specifies the amount of memory that one user context can allocate to the R/3 Extended Memory. Valid for all types of work processes.

The value refers to the R/3 Extended Memory that a user context allocates. If the value entered is exceeded, heap memory is allocated. The work process is assigned exclusively to this user context and is no longer available for other user contexts since it is switched to the PRIV mode (in the work process monitor, Transaction SM51). See: Private Memory

If the value is set too high, caused by a large user context, an Extended Memory bottleneck can occur. If a large user context fills the R/3 Extended Memory, other smaller user contexts could thereby switch work processes into PRIV mode before their R/3 Extended Memory limit has been used up.

SAP recommends that you test your system using the high default value (250 MB). If the PRIV mode is switched on prematurely, you can decrease the size to the recommended value.

Under IBM AIX and Siemens-Nixdorf SINIX, you can use parameter ztta/roll_extension to balance the effects of the relatively low values that you can set for abap/heap_area_nondia (see abap/heap_area_nondia: Heap Memory Limit for Non-Dialog Work Processes and Data Segment Sizes (UNIX)). On these platforms, the relatively small values for the maximum data segment size limit the heap memory available for background job processing.

In order for the background processing to have at least 500 MB memory allocated to it, SAP recommends setting the parameter ztta/roll_extension to the values listed below. Set these values only on the servers that are used primarily for background processing. Otherwise, the R/3 Extended Memory may be filled by just a few work processes and the PRIV mode will be switched on prematurely (see Recognizing and Correcting Problems).

• AIX values for background processing: > 300 MB
• SINIX values for background processing: > 200 MB

In order for the active processes to be executed, you must increase the value for em/initial_size_MB: Extended Memory Size. You can determine the amount of Extended Memory your servers allocates by using Transaction RZ03 (see Overview of All Application Servers). The peak value displays the "high water mark" (maximum allocation) for Extended Memory.

Under AS/400, you can increase the value as needed to enable the processes to use more Extended Memory.

Goal:

Minimize the number of dialog work processes in the PRIV mode.

Integration

• em/initial_size_MB: should be significantly larger than ztta/roll_extension.
• ztta/roll_area: a higher value saves on R/3 Extended Memory.
• rdisp/ROLL_SHM, rdisp/ROLL_MAXFS: If you increase the value of ztta/roll_area, you must adjust these parameters

Activities

Unit: Bytes

Default value: 250000000 (250 MB)

20971520 (20 MB) under AS/400

Recommended value: 500000000 (500 MB)

Changes: Customers can make changes. You can find the values from the configuration examples (Contents button).