Determining Swap Space Requirements (UNIX)

The program sappfpar lets you check the minimum and maximum (worst case) swap space requirements for an SAP application server. It also checks the shared memory requirements and whether or not the parameters em/initial_size_MB and abap/heap_area_total are set correctly. Proceed as follows:


       1.      To check the instance profile for the SAP application server, start the SAP program sappfpar from the UNIX command line. Enter the following command:

/usr/sap/<SYSTEM NAME>/SYS/exe/run/sappfpar check pf=/usr/sap/<SYSTEM NAME>/SYS/profile/<Profile name> nr=<System number> name=<Systemname> | more

       2.      The program generates a list. Note the total value for the shared memory in the field Shared memory under Memory requirements estimated. This value corresponds to the size of the shared memory required for this profile, and must be calculated into the shared memory requirements for the new Memory Management.

       3.      At the end of the list, the program specifies the minimum swap space requirements, the maximum heap memory requirements and the swap space requirements in a worst case scenario:

Total, minimum requirement.....:  169.5 MB (shared memory requirement)
Process local heaps, worst case:  762.9 MB
(is set with abap/heap_area_total)
Total, worst case requirements: 
962.5 MB

Ensure that there is more swap space available than what is specified in the worst case scenario. (This is because non-SAP processes also require swap space.)

For optimal performance SAP recommends the following swap space:

·        20 GB on 64 bit systems

·        3-6 GB on 32 bit Linux

Why do I need 20 GB of swap space?

64-bit technology means that the address space can now be used more generously. This minimizes maintenance requirements and the problems associated with memory management, since the size of the buffers and other areas in the shared memory can be increased considerably so that programs do not reach the system limits.

As a result, there is no risk of program crashes due to memory bottlenecks and no need for complex 'parameter tuning'.

Large parameter values and address spaces do not automatically mean more main memory is required. The main memory required is determined by the extent to which the configured areas are actually used.

The additional swap space requirements may be higher for application servers where heavy online operations and background jobs with large data volumes alternate (day/night operation).

Expanding the swap space may require additional disk space in certain circumstances. This is highly recommended due to inexpensive hardware prices.

Independent of the swap space size, you should monitor the swap space itself to avoid bottlenecks.