on 06-19-2008 8:44 PM
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
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
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