Swaps observed in ST02

[Former Member]

Hi Friends,

In my ECC production system, ECC 6.0, AIX 5.3, Oracle 10g. I have observed a lot of swaps in ST02,

Can someone give me guidelines understanding the impact of this, why does this happen and how to improve and ensure that the situation does not occur.

Thanks

Aliila

[Former Member]

Some Memory Settings to Help with Swaps...

If you are running a Central Instance on a server that is also hosting the database, you may run into a problem with high swaps as seen in transaction ST02. The problem is that typically when SAP is installed, the default settings will allocate all of the system memory to SAP, leaving nothing for the database or other applications that may be running on the server. This will mean your page file will need to be very large (sometimes 3x the amount of system memory) in order for SAP to even start up.

If you are in this situation, try the following:

First, you will want to dictate to the database how much memory to use.

With SQL Server 2005, I prefer to allocate 6 GB of system memory as long as the system has 16 GB or more installed. SQL Server Management Studio is the tool to use to do this. Check with your RDBS guidelines to see how much your database host is required to have available and do not go under that.

Secondly, you will need to decide how much memory to assign to SAP.

You can assign the balance of the system memory to SAP, but if you have other applications that run on the system you will want to take that into consideration as well. In a system with 16 GB of memory that has 6 GB dedicated to the DB, I assign 10 GB of memory to SAP. This is done so by setting the PHYS_MEMSIZE parameter (MB) in the Instance Profile. I have a few systems with two Central Instances installed on the same 16 GB server, so I assign 6 GB to SQL Server, and 5 GB to each SAP instance.

Third, if you are still getting high swaps in ST02, you will want to look at the settings of each buffer parameter.

Inside ST02 under the "Current Parameters" button you will find what parameter settings you are running with. the defaults are supposed to be a good starting point for the typical SAP install, but here are the parameters I like to set:

rsdb/ntab/ftabsize = 60000

rsdb/ntab/entrycount = 40000

rsdb/ntab/irbdsize = 12000

rsdb/cua/buffersize = 6000

rsdb/obj/buffersize = 8192

abap/buffersize = 600000

zcsa/table_buffer_area = 60000000

zcsa/presentation_buffer_area = 8800000

Using these settings I rarely get high swaps in my SAP systems, but you will need to study each parameter and tweak them for your specific install.

I hope this helps...

http://joeybear23.blogspot.com/2008/10/some-memory-settings-to-help-with-swaps.html

[pavan_kumargali]

Hi Aliila,

Among all the buffers, PXA (program buffer) is very important. If you see swaps daily more than 10,000--> which means really issue.

Also for other buffers, if you see more swaps are occuring daily with RED marked swaps,

then you need to take care of the buffer parameters.

We recommend you to increase atleast 10% to the current values.

However for Program buffer you may increase 20% also.

hope this helps!!!

Thanks and Regards,

Pavan Kumar Gali.

[Former Member]

Hi Aliila.

If too many swaps are happening in your system that means buffer is getting full for particular parameters.check the hit ratio for each buffer,it should be greater than 95% after that double click on the parameters which are showing red swaps and analyze. Check swap space configured in your system it should be 2.5 times your present RAM. Are you facing any performnace issue ?If not no need to worry once you will restart ur server therse swap values will become zero.

You can increase the buffer parameters values by 10%.

Regards,

Prashant

[Former Member]

Hi,

When a buffer has insufficient freespace or free directories, it has to swap objects out of the buffer in order to load a new object. The column Swap shows how many objects have been swapped out since system startup.

Please refer

http://help.sap.com/saphelp_47x200/helpdata/en/fb/cbb96cd9ee11d188be0000e83539c3/frameset.htm

Cheers

Deepu.

Edited by: Deepu Rajendrababu on Oct 7, 2008 7:14 AM

[Former Member]

Hi,

You need to check the SAP buffer parameter, whether this are set appropriately,

For example for setting Name tab buffer sizes check OSS note:16244,

In general for SAP Parameter recomendation check OSS note:103747

Regards,

Vijay.