Preventing Swap-Space Bottlenecks (UNIX)

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 SAP application server.

Consider the following parameters:

Parameter

Limits the amount of process-specific memory used...

abap/heap_area_dia

...by any particular dialog work process

abap/heap_area_nondia

... by any particular non-dialog work process (background, spool, etc.)

abap/heap_area_total

...by an SAP application server -- all dialog and non-dialog work processes

You can find more information on the functions of these parameters under Limits for Allocating Heap Memory in Functions of the SAP 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 SAP 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.

For further information, see Swap Space Bottleneck During SAP System Operation.