cancel
Showing results for 
Search instead for 
Did you mean: 

Observation: SAP uses swap space even when OS has available unused memory

Former Member
0 Kudos

Hi Folks,

It is my understanding that any memory not used by the Linux OS itself or the SAP application is available for Linux to use for I/O buffers and file caching. When the SAP application requires more memory I would expect Linux to take memory away from itself (release I/O buffer and/or file caching memory).

We have observed that SAP uses swap space even when there is memory available. Is there some feature in SAP kernel or some ABAP construct that causes SAP to prefer swap space over available memory? Or maybe there is a Linux kernel setting that influences SAP's use of swapping.

Regards,

Zaz

Accepted Solutions (0)

Answers (1)

Answers (1)

Former Member
0 Kudos

Hi Mike

You did not mention which distribution you have. Under SLES there is is a parameter called SWAPPINESS, which controls the buffering/swapping.

cat /proc/sys/vm/swappiness

If you don't already know, you can see the memory usage with the free command.

root # free -m
             total       used       free     shared    buffers     cached
Mem:          7987       7901         85          0        364       4262
-/+ buffers/cache:       3274       4712
Swap:        15999          0      15999

As far as i know, in this example 3274 is memory used by SAP and other processes and 4712 is cache. Please correct me if i am wrong.

Regards

Michael

Edit: a low swappines, for example 10 means to reduce cache first, a high swappiness (example 100) means page out processes first

Edited by: mho on Jun 20, 2008 11:21 AM