Many SwaP entries found on ST02

[Former Member]

Hi Team,

When i perform a weekly helath check on production system.I found that many swap entires are popping up in red and also users feeling that system is running bit slow since few days. Can some one please help us in indentifying the issue and sugegst us on fixign this issue.

Buffer Hitratio Allocated Free space Dir. size Free directory Swaps DB [%] [kB] [kB] [%] Entries Entries [%] accesses

Nametab (NTAB)

Table definition 98.09 6,330 2,494 43.73 20,000 8,745 43.73 0 11,993

Field description 95.61 30,859 5,609 18.70 20,000 15,964 79.82 15,157 19,756

Short NTAB 97.05 3,332 2,830 94.33 5,000 4,470 89.40 0 530

Initial records 92.49 6,332 974 16.23 5,000 1,466 29.32 13,182 16,716

Program 98.06 400,000 737 0.20 100,000 91,336 91.34 31,726 121,302

CUA 98.67 3,000 108 4.31 1,500 1,246 83.07 11,581 856

Screen 98.06 4,297 4 0.12 10,000 9,632 96.32 301 1,404

Calendar 99.76 488 359 75.10 200 48 24.00 0 152

OTR 100.00 4,096 3,439 100.00 2,000 2,000 100.00 0 0

Tables

Generic key 99.04 29,297 2,606 9.34 5,000 1,092 21.84 133 42,758

Single record 93.87 10,000 2,765 28.07 500 337 67.40 0 18,068

Export/import 81.17 4,096 137 3.98 2,000 730 36.50 37,036 0

Exp./Imp. SHM 92.22 4,096 3,301 95.99 2,000 1,996 99.80 0 0

Do i need modify any memory parameters on my system? Please see the memory parameters configured on servers as follows

Program buffer:

Abap/buffersize 400000 kB

Screen Buffer:

Zcsa/presentation_buffer_area 4400000

Sap/bufdir_entries 10000

Screen buffer

zcsa/presentation_buffer_area 4400000 Byte

Sap/bufdir_entries 10000

Export/import buffer

rsdb/obj/buffersize 4096 kB

rsdb/obj/max_objects 2000

rsdb/obj/large_object_size 8192 Byte

rsdb/obj/mutex_n 0

Few other :

abap/heap_area_dia 2000000000 Bytes

abap/heap_area_nondia 2000000000 Bytes

abap/heap_area_total 5000000000 Bytes

abap/heaplimit 40000000 Bytes

em/address_space_MB 512 MB

Thanks & Regards,

Vinod

[Former Member · Accepted solution]

Hi,

SAP buffers store frequently-used data, and make this data available to the local application server instance.

The fact that each application server has its own buffers could result in data inconsistency across the various application servers (instances). To prevent data inconsistency, the SAP System uses periodical buffer synchronization, which is sometimes called buffer refresh.

http://help.sap.com/saphelp_nw04s/helpdata/en/c4/3a6dd5505211d189550000e829fbbd/frameset.htm

there is no general rule for increasing buffer parameters. You need to keep on monitoring & then fine tune all buffers.As a thumb rule we generally increase 20-25% of what they are now but it all depends on swapping.Also consider hit ratio,for most of the buffers it should be around 99% except program buffers.

Buffer synchronization is required only for distributed SAP Systems when more than one application server (instance) is used. If your SAP System utilizes only one application server (instance), buffer synchronization is not needed. When the application server is restarted, all buffers are erased and dynamically reconstructed.

Resetting buffers can significantly change the performance of the entire system for a long time. It should therefore only be used where there is a good reason to do so.

/$SYNC This resets all buffers of the application server

/$CUA This resets the CUA buffer of the application server

/$TAB This resets the TABLE buffers of the application server

/$NAM This resets the nametab buffer of the application server

Have a look at this link:

http://help.sap.com/saphelp_nw04s/helpdata/en/c4/3a6dd5505211d189550000e829fbbd/frameset.htm

Restarting the buffer also cleans up the buffers. Sometimes resetting the buffers may lead to skipping of number ranges in certain transactions. But its very rare. And when buffers are reset, some transactions may take more time for it to be executed as it has to fetch the data from database. (its the same case if you restart the server).

Hope this helps you.

Thanks

Sushil

[anindya_bose · Accepted solution]

Not all the buffers are important for system performnace. You might need some buffer tuning for the buffers which are important for system performance. Look for the hit ratio for program buffer. This is the most important for system performnace. You might tune the below SAP parameter and then restart your application.

rsdb/ntab/ftabsize

rsdb/ntab/entrycount

rsdb/ntab/irbdsize

abap/buffersize

[Former Member · Accepted solution]

Hi Sushil,

I have posted memory configuration details in my earlier post and also i restarted my production server However i see buffer entries are appearing and increasing in ST02 transaction. Based on the values specified can you please suggest what are the values needs to be changed and at what extent i can go and also i would like to know how to identify the parameter dependeces before i go-ahead and change any memory parameters.

Most of the buffer entires i found was with program buffers, NTAB Buffers, CUA ,Screen , Calander and Export and Import.

Buffer hit ratio is 83.33 % i believe which shoud not be less than 95 %. Please help us in analysisng the issue.

would be much appreciable for any suggessions.

Thanks & Regards,

Vinod

[markus_doehr2 · Accepted solution]

Buffer tuning is an iterative process.

It heavily depends on how the system is used (how many different programs are accessed etc.)

I would increase the values by 50 % and restart the system and watch it for some days, if it's not sufficient, I'd increase the values again.

Markus

[Former Member]

Problem resolved temporarrily by incerasing program buffer.thanks for all your suggessions.

[Former Member]

Vinod,

Thr is no fix formula related to buffer size. e.g. program buffer value is 300 MB try by changing it to 350-400 & monitor. This way you can reduce the swaps.

Thanks

Sushil

[Former Member]

Hi shushal,

Sorry for the delay in getting back you.

As Suggested, I have changed the few of buffer parameter values by 20 % (EXPORT / IMPORT Buffer) , Earlier it was configured to 4096 KB and MaX objects value was 2000. By keeping on increasing the values and now it is 9600 KB . Almost i have double the value however still More swaps are occuring as earlier. No change...!

Today i have checked the system and found 62,138 Swaps only for Export buffer . Can you please suggest, Still do you want me to increase the parameter values untill unless the swaps come down. or is there any limitation. I know it's all based on memory configured on SAP system ( Currently system running on 6 GB of RAM and also we have Changed the Paging Memory from 12 GB to 18 GB last week and restarted the system. but No luck .

But i don't see any major performance issues , Dialog and Background responses are fine as expected. Still many swaps are in red for Table Buffer,CUA , SCREEN and Program Buffer.. etc.

System Configuration: ECC 5.0 , WINDOWS 2003 ,SP2 + SQL 2000 DB

Current Values:

rsdb/obj/buffersize 9600 kB Size of export/import buffer

rsdb/obj/max_objects 4800 Max. number of objects in the buffer

rsdb/obj/large_object_size 8192 Byte Estimation for the size of the largest objec

Hit Ratio : 89.40 %

Old Vlaues:

rsdb/obj/buffersize 4600 kB Size of export/import buffer

rsdb/obj/max_objects 2000 Max. number of objects in the buffer

rsdb/obj/large_object_size 8192 Byte Estimation for the size of the largest objec

Thanks much for any help.

Best Regards,

Vinod.

[Former Member]

Watch it for a day and increase by 20% again.

[Former Member]

Hi Every one,

Thanks for all your inputs.

As Suggested we have restarted the production server however identified many swap entries red as fllows( Field Description- 30,970, intial Records- 26,169, Program Buffer - 71,628, CUA- 30,442, Screen - 826 ) and Tables Generic Key - 389 & Export / Import - 247,144 )

I see that Buffer Hit ration of EXport / Import is 83.93 except this all other buffers are above 99 % .

Below are my system configuration details:

OS: WIN - 2003

SAP Version : ECC 5.0

Main Memory Configured : 6 GB

Paging Memory : 15 GB

Memory Parameters :

rsdb/ntab/ftabsize 30000 kB Size of field description buffer

rsdb/ntab/entrycount 20000 Max. number / 2 of table descriptions buffered

• FTAB needs about 700 bytes per used entry **

Initial record buffer IRBD

rsdb/ntab/irbdsize 6000 kB Size of initial record buffer

rsdb/ntab/entrycount 20000 Max. number / 2 of initial records buffered

• IRBD needs about 300 bytes per used entry **

Program buffer PXA

abap/buffersize 400000 kB Size of program buffer

abap/pxa shared Program buffer mode

CUA buffer

rsdb/cua/buffersize 3000 kB Size of CUA buffer

The number of max. buffered CUA objects is always: size / (2 kB)

Generic key table buffer TABL

zcsa/table_buffer_area 30000000 Byte Size of generic key table buffer

zcsa/db_max_buftab 5000 Max. number of buffered objects

Export/import buffer EIBUF

rsdb/obj/buffersize 4096 kB Size of export/import buffer

rsdb/obj/max_objects 2000 Max. number of objects in the buffer

rsdb/obj/large_object_size 8192 Byte Estimation for the size of the largest object

rsdb/obj/mutex_n 0 Number of mutexes in Export/Import buffer

Based on the above information, Could some one please help me in tunning the memory parameters ( i.e at what extent i can increase / Decrease ) as i was doing this first time.

Would be much appreciable if some could throw some light on this issue.

Many Thanks,

Vinod

[Former Member]

Hello,

Can you check when was the system last restarted?You get this information in st02.

As the system usage increases, so does the swap count because of the movement of the buffers(LRU).

I would say, initially going with you can try a system restart and check usage per day.

Out of all the buffers, the program buffer is the one which is read more.If the usage of buffers increases heavily, then you have to check the buffer sizes.

You have some information related to buffers here:

http://help.sap.com/erp2005_ehp_04/helpdata/EN/c4/3a6e98505211d189550000e829fbbd/frameset.htm

Buffer tuning:

http://help.sap.com/erp2005_ehp_04/helpdata/EN/c4/3a6e98505211d189550000e829fbbd/frameset.htm

Hope it helps,

Thanks,Prasanna

Edited by: Prasanna K on May 22, 2009 10:42 PM