How does SAP Use memory?

[andre_jansevanrensburg]

Hi all

Most musty think this is a stupid questions but i just need some clarification

We running SAP ECC 6 on AIX 6.0

I have 16 GB physical memory

Inst06 i see that there is less than 500 mb free, What does this mean.

My swap space is not being used at all

Is SAP Using All of the 16 GB or is it just occupied.

Am i running low on memory and need to upgrade or is this normal

Thank you.

[Former Member]

Dear Andre,

AIX is using memory in a different way if you have parameter ES/TABLES = SHM_SEGS (which you should).

[http://wiki.sdn.sap.com/wiki/display/SI/MemoryAllocationand+Analysis]

So you should only use AIX specific documentation if you want to learn about it.

AIX also uses memory for interal needs if available, so if your server is not swapping you should be fine.

Kind regards,

Gerd

Edited by: Gerd Kirchner on Jan 18, 2012 9:23 AM

[Former Member]

Hello Andre,

Its Hard to say that your system is not utilizing your SWAP without checking ST02 buffer analysis and your profile parameters.

Since how many days you are facing Performance Issue in your SAP system ?

Any activities are done at SAP System (Application Server) level ? Database Level ? Os Level ?

Tuning of OS, DB and Application layer should fix your issue and Performance Analysis, Tuning & optimization is ONGOING Process.

You will need to go through the following REFERENCE SAP Notes to compare existing Parameter values set in your SAP Landscape.

Note 921196 - AIX Memory Tuning Recommendations >5.2

Note 146289 - Parameter Recommendations for 64-Bit SAP Kernel

Note 425207 - SAP memory management, current parameter ranges

Note 1171650 - Automated Oracle DB parameter check

Also run SAPPFPAR check to analyze your memory buffers

http://help.sap.com/SAPhelp_nw70/helpdata/en/66/380fb7d43d11d188bd0000e83539c3/content.htm

Regards,

Arjun

[andre_jansevanrensburg]

Hi guys

Thank you so much for the information.

There aren`t really any performance issues.

On checking st02 my program buffer is swapping a little bit and that's all 4914 kb

I just want to find out more on how the system uses memory as i did not set it up in the beginning.

We are planning to go to unicode soon and i need to evaluate if i need more memory installed or not for the conversion.

Thank you

Regards

[Former Member]

Hello Andre,

I suggest you to go through the history of memory utilization on all application serers in ST06 (Detailed Analysis) in order to decide on memory expansion.

Thanks,

Siva Kumar

[Former Member]

HI,

If you have 16 GB memory allocated and you see 500 MB free then definitely you have to tune your memory parameters in the system depending on resources available.

Please check ST02 as well for checking detailed usage of Roll,Page,heap and extended memory components.

You dont see swap space utilized,mostly because of the reason being you have high em/initial_MB value allocated for WP.

swap will be used once WP start using heap memory segment and start going into PRIV mode.

Check this help doc for more understanding on heap memory

http://help.sap.com/saphelp_nw04/helpdata/en/02/96253c538111d1891b0000e8322f96/frameset.htm

Regards,

Ashutosh

[Former Member]

Hello Andre,

You need to analyze which process is consuming more memory. I suggest you to go through the below link for more details on swap space and free memory.

http://help.sap.com/saphelp_nw04/helpdata/en/55/b5b93b5bb3493fe10000000a114084/frameset.htm

Thanks,

Siva Kumar