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Virtual memory required by SAP system component?

Hi experts,

  ok, ok, I know there is already a link mentioning this Virtual Memory Required by SAP System Components

I just want to confirm this sizing is correct. According to Cameron's guidance(note 1612283), 2 * E2680(16 cores) and 384 GB DRAM can run 6-8 dialog instances per server. Karl-Heinz Hochmuth recommends

Page file sized needed = total virtual memory - RAM and

ABAP dialog instance = 2 times PHYS_MEMSIZE.

  That's to say, if I have 384GB DRAM, I should allocate about 384GB pagefiles size for 6-8 SAP dialog instances(each instance with PHY_MEMSIZE=32000) and that's sufficient, right?

  I remember SAP recommended pagefiles size should be 3x - 4x of physical memory size before and that is invalid now, right? Also, It is not necessary to allocate very large pagefiles even though I have 8 SAP dialog instances running concurrently, correct?

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2 Answers

  • Best Answer
    Jan 05, 2015 at 08:59 AM

    Hello Dennis,

    some questions about your sizing:

    How many dialog instances do you want to run in parallel on one Windows system?

    Which Windows version do you plan to use?

    Virtualized or on a physical box?

    How many CPU cores do you have? (Hyperthreading turned on)

    How much RAM do you have?

    How many work processes do you plan to use (per dialog instance)?

    Test / dev systems or productive usage?

    Best regards,

    Karl-Heinz

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    • Hello Denis,

      the answer is: Yes a 384 GB pagefile should be sufficient. You can check this anytime, e.g. with the "systeminfo" command. There you will find information how much RAM is currently used and how much virtual memory is currently used.

      You can also use TaskManager or tools from www.sysinternals.com - of course.

      One comment to your old configurations:

      If you want to add another SAP dialog instance on a Windows OS where already one SAP instance is running you MUST specify the PHYS_MEMSIZE parameter in instance profile. This will be made e.g. if you upgrade a SAP system, a so called "shadow instance" will be installed during upgrade and this instance will be usually run with PHYS_MEMSIZE = 50%.

      If you don't set PHYS_MEMSIZE to a lower value than RAM, than it is EQUAL to RAM.

      Which means, that you need huge pagefiles to simply START your instances.

      This has something to do with the SAP memory model and how memory address space will be allocated AND reserved.

      Best regards,

      Karl-Heinz

  • Jan 05, 2015 at 08:36 AM

    Hi Lee

    Depend on your SAP system usage & requirements. At the very beginning time you can define the pagefile size for each VM should be 1.5 to 2 or 2.5 max time of physical memory(32 GB per vm). depend on usage you can either add more or reduce the size of the pagefile. and also you can refer the SAP Note for other parameters

    88416 - Zero administration memory management for the ABAP server


    BR

    SS

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