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Former Member

Many SwaP entries found on ST02

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

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5 Answers

  • Best Answer
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    Former Member
    May 22, 2009 at 09:22 PM

    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

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    • 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

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    Former Member
    May 22, 2009 at 08:40 PM

    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

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    Former Member
    Jun 03, 2009 at 09:40 AM

    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

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    Former Member
    Jun 02, 2009 at 12:21 PM

    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

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    Former Member
    Mar 05, 2010 at 11:43 AM

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

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