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Former Member

used memory WP

HI,

I have a few questions regarding memory management in SAP system.

I read about it a lot butI still confused 😕

My question is:

1. How I know how much memory all the WPs is used? (How much memory all the WPtakesfrom the OS)

2. How I know how much memory all the DIA's is used? (How much memory all the DIAtakesfrom the OS)

Idontwantseperateit to extend memory roll areaetc, I want to know percentage of memory all the WP takes from the OS.

I asked it becauseineed to increase the number of DIA in the APO system, but before the change I want to know how much memory the WP and the DIA used now, I want to avoid frommemory problemin the OS afteriincrease the number of DIA.

My server is always around 80% memory used, but I limit the memory used bySAP systemwith the parameter PHYS_MEMSIZE, and Idontthink the SAP takes all the PHYS_MEMSIZE parameter value.

And it'stakeme to the 3 question:

3.howI know how much memory the SAP system takes fromOS? I limit the memory used by SAP with PHYS_MEMSIZE, but I want to know exactly how much memory the SAP takes and if he used all the valueigive in the PHYS_MEMSIZE.

Maybe Idontneed to increase memory in the server just to increase the number of DIA

Thanks for your help my freinds 😉

Naor

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5 Answers

  • avatar image
    Former Member
    Oct 21, 2015 at 06:51 AM

    HI.

    First Iwant to thanks for your help

    So if I understandcorrect thereis no way to know what is exactly the used memory of the WP\DIA?

    And what about the all SAP memory?

    I ask you another question.

    Let's say you need to increase DIA in your sap system. whatdo you check before you do it, from the memory side, to be sure you will not have memory issue.

    Thanks Naor

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    • Hello Naor,

      Use this formula. There are minuses as well.

      Total Memory Used by SAP & DB =

            DB memory  (rule of thumb 1/3 of Host memory)  +

            (Total Alloc KB in ST02 – Total Freesp. KB in ST02) +

            Roll Area Max Use in ST02 second table +

            Page Area Max Use in ST02 second table +

            Extended Mem Max Use in ST02 second table +

            Heap Memory Max Use in ST02 second table

      Can you send your ST02 as screenshot and as text also. And current memory parameters. I will try to calculate it for you.

      Regards,

      Yuksel AKCINAR

  • Oct 20, 2015 at 04:14 PM

    Hello Naor,

    Each work proess will use some memory just to "exist" in the system (something around 100MB - 200MB, depending on the SAP kernel release in use).

    Besides that, I believe you can use the sappfpar output to have an idea of how much memory SAP will use.

    You can execute this tool at operating system level (notice that the "pf=..." argument has to be adjusted):

         sappfpar check pf=/usr/sap/SID/SYS/profile/instance_profile

    Keep in mind that sappfpar will not account the "heap memory" (parameter "abap/heap_area_total").

    The heap memory is allocated and freed dynamically, as the system needs.

    Regards,

    Isaías

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  • Oct 20, 2015 at 05:45 PM

    Hello Naor,

    As you may know ST02 Tx is the place where you need to check about memory usage in SAP instance.

    Let me try to explain the topic with some parameters and formulas;

    Here is the total memory usage for an SAP System including DB. Maximum usage of the memory can be found using this formula.

     

    Total Memory Used by SAP & DB =

          DB memory  (rule of thumb 1/3 of Host memory)  +

          (Total Alloc KB in ST02 – Total Freesp. KB in ST02) +

          Roll Area Max Use in ST02 second table +

          Page Area Max Use in ST02 second table +

          Extended Mem Max Use in ST02 second table +

          Heap Memory Max Use in ST02 second table

    You cannot calculate the max usage of memory using dia or non-dia wps count because all wps use a shared extended memory. There are parameters to limit the usages of this extended memory for each wp like ztta/roll_extension. You can check the usage and allocation of these parameters in ST02 transaction.

    SAP keeps local memory of each wps very small in order all wps to use shared memory. For performance and usage reasons.

    One more thing that needs care is;

    Under normal conditions heap area usage is not accepted. If a wp is using heap memory it means it is in PRIV mode. And using unshared memory area. This is not wanted. This is limited with abap/heap_area_total parameter.

    You can check below link for a presentation.

         SAP Memory Management

    Regards,

    Yuksel AKCINAR

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    • Former Member

      Dear Yuksel

      You can help with this:

      DB memory  (rule of thumb 1/3 of Host memory)  + ST04?

      (Total Alloc KB in ST02 – Total Freesp. KB in ST02) + where ifind this in ST02? thefirst table?

  • avatar image
    Former Member
    Oct 21, 2015 at 08:14 AM

    HI

    Buffer             HitRatio %  Alloc. KB Freesp. K

    Nametab (NTAB)

      Table definition     99.96     25,211     11,881

      Field definition    100.00    125,861     73,304

      Short NTAB          100.00      6,321      3,222

      Initial records      98.74     37,345     29,911

    program                99.92  1,800,000    686,254

    CUA                    99.97     13,000      1,179

    Screen                 99.98     19,532      1,757

    Calendar              100.00        488        316

    OTR                   100.00      4,096      3,327

    Tables

      Generic Key         100.00    200,000     27,451

      Single record        97.36     40,000     10,857

    Export/import          98.46     75,000     10,907

    Exp./ Imp. SHM         99.57      4,096      2,178

    SAP Memory      Curr.Use % CurUse[KB] MaxUse[KB]

    Roll area            1.21      3,175     11,784

    Page area            0.45      1,183    262,136

    Extended memory      2.72    913,408  6,385,664 

    Heap memory                        0  2,244,228

    PHYS_MEMSIZE                                25600

    total memory - 32 GB

    Oracle  - 17 GB

    Thanks

    naor


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  • Oct 21, 2015 at 01:21 PM

    If you increase the number of work processes for an instance then you should make sure there is enough memory on the machine and if not you should increase memory (RAM). Like Isaias said every process will need memory from the OS to exist. It is not just for SAP work processes, any process/activity running on a machine will need memory. As you have an Oracle database when you increase work process you should increase the processes and sessions parameter. This means you should consider memory for Oracle processes. The recommendation from SAP is to consider 250 MB per work process but I would say 250 MB is quite a lot and maybe SAP is suggesting it as a defensive strategy. I normally check the ST02 detailed analysis for information about memory used by each work process. The parameter PHYS_MEMSIZE will limit the memory to be used by the SAP system.

    Virtual Memory Required by SAP System Components

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