ST02 SWAPS reported what does that mean.

[Former Member]

Hi Team,

In ST02 of one of the system all the apps I see many SWAPS column with value and in red color, what it mean

program, swaps with 11,349

generic key with 68

single record with 1,002

Thanks

Vijay

[Former Member · Accepted solution]

Hi Vijay,

A few guidelines to monitor/control the buffers with ST02:

Object swaps

Always aim for zero swaps

Exception: program buffer. Here some swapping will almost always happen. As mentioned in an earlier reply, 10000/day is the upper limit.

Free space in buffer

Monitor the buffers regularly with ST02. If the free space % (or the free dir %) falls below 15-20% (exception is again the program buffer, which will probably have ~0% free), then increase the profile parameter for the buffer size in RZ10. There is normally no need to restart the system immediately, you can wait until the next planned downtime window.

Note for export/import buffer

Make this buffer much bigger (10 times bigger or more) than the default. If this buffer overflows you will see an explosive increase in the number of swaps (sometimes hunderds of thousands over a short period of time). Also increase the directory size to a value equal to 30-50% of the buffer size, e.g. rsdb/obj/buffersize = 40000, rsdb/obj/max_objects = 15000.

In BI systems do the same for the Exp/Imp SHM buffer.

Regards,

Mark

[Former Member]

Dear , Wong

My Server in ST03 ,

Task Type Ø Load- + Gen. Time

AUTOABAP: 84.7

AUTOTH: 0

BACKGROUND: 8.8

BUFFER SYNC: 0

DDLOG CLEANUP: 0

DEL. THCALL: 0

DIALOG: 5.1

RFC: 5.8

RPCTH: 0.3

SPOOL: 1.3

UPDATE: 7.9

UPDATE2: 3.8

Task AUTOABAP Load and Gen Time up to 84.7 , please advise me.

Thank.

[former_member447076]

Hi,

ST02 is the buffer monitor that offers instance specific information that provides:

1. status of different buffers instance wise

2. information on memory usage instance wise

3. information on table buffering at instance level

Swapping takes place for two reasons:

1. not enough 'free space left' in buffer for buffering new objects

2. buffer has run ouf of 'free directory entries' that can be contained in one buffer area *

• Directory entries diminish the available size of the buffer, independent of their usage.

Swaps are to be avoided, as are all other situations leading to lines shown in red in the ST02 display.

Please note that Buffer swaps occur when buffer content is deleted from the buffer and is replaced by other content. It has no relation at all to the swapping mechanism on OS level.

An example with a more practical outlook to swapping observed:

Use transactions SM50, ST03N and ST02 to identify the problem.

a. Using SM50 you might find high number of work processes accessing tables related to ABAP sources and status as 'Load Program'. This hints to a problem with Program [PXA] buffer.

b. In transaction ST03N, you find unusually high 'load and generation time' causing even higher wait times. Threshold for load and generation time is typically 50 ms.

c. In buffer monitor i.e. ST02, you find many swaps [typically more than 10000 swaps happening per day for program buffer]. Check on hit ratio [value below 95% is typically poor]. This indicates problem. Program buffer could be small!!

If program buffer is small, it means that workprocesses require to reload program loads over and over again which causes bad system performance.

Resolution: Increase program buffer size/ check on load and generation times/ hit-ratio increases/ system response time also lowers down!! : )

Regards,

Shabnam.

[Former Member]

Hi bijay,

Could u pls. help me to understand the facts happening for me here. In my system, observing, though there are some free space, also directory entries available yet there are some swaps records. why like this? any documents for this available, if so please, give me its address.

thanks in advance,

Kafi,

[Former Member]

Hi K.M.,

You might have free space, but if that space is for eg 100 and the object that it needs to load into the buffer is 200 in size, the buffer will have to clear some more space to load the object. How much space do you have free? Also look at the history of the buffer, as the buffers are counting since system start and you might have old swaps but not new ones. No more that 10,000 a day is a good rule of thumb. Also don't worry too much about it unless you have a considerable number of swaps or or performance is being affected by it.

Regards

[Former Member]

Hi

The no. of swaps increase due to the following reasomns::

Buffers set too small.

The required data cannot be stored in the buffers. Instead, objects have to be swapped out of the buffers. This causes expensive database accesses.

Buffers set too large

Memory is wasted. Paging may occur if too much memory is taken from the operating system and allocated to the SAP buffers and database.

The following link would give you all the information you need on Buffers.

http://help.sap.com/erp2005_ehp_04/helpdata/EN/c4/3a6dbb505211d189550000e829fbbd/frameset.htm

Regards

Chen

[Former Member]

Hai,

Normally in SAP the buffers are used to store the SAP object/data from DB. This is done for easy access of data when the users need them, it helps to increase the performance of the system by decreasing the I/O of system i.e, when the user requests data the work process first checks the buffers for the data requsted by the user, if it finds it there then it returns to the user with the data thereby increasing the speed of the access and in turn the performance. If the data is not found in the buffer a physical access to DB is made thereby increasing the response time and lowering the performance. After the data is fetched and returned to the user a copy of the data is put into the buffer, this helps to increase the access when some other user requests the same data as said above.

This mechanism is accomplished when you have a better buffer size, if your buffer size is very small the data put into the buffer will be pushed out to accomodate the new data, the red color indicates the no.of objects swaped out from the buffer to accomodate the new object in the buffer.

In your case the buffers needs to be increased to accomodate more objects in them, keep in mind that performance tuning needs more analysis and skill.

Changing Buffer parameters involves more calculations and might lead to poor performance if done wrongly or prevent the system to start since you have to restart the system in order to make the profile parameters related to buffers active.

Please check the below links to optimize your buffer quality and decrease the swaps....

http://help.sap.com/saphelp_nw04/helpdata/en/c4/3a6e98505211d189550000e829fbbd/frameset.htm

http://help.sap.com/saphelp_nw04/helpdata/EN/02/9625e3538111d1891b0000e8322f96/frameset.htm

http://help.sap.com/saphelp_nw70/helpdata/EN/bc/4a813b680c250fe10000000a114084/content.htm

Regards,

Yoganand.V

[Former Member]

Hi,

There will be some swaps in the program buffer. The important points are the hitratio (should be up to 98%) and the 'load & gen.time' in Transaction ST03 (should be less than 10ms). If these values

are OK, then the swaps don't matter.

The number of swaps should be low. EXCEPTION: The program buffer will show swaps. Here the general rule is, that you should not observe much more than 10000 swaps per day. If you do not observe that 10000 swaps per day, the situation is not critical.

Cheers