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Wednesday, 10 August 2011

Memory allocation sequence to dialog work processes in SAP

This article answers the following queries:
  • What is the memory allocation sequence to dialog work processes in SAP?
  • When does a work process go to PRIV mode?
  • How to avoid or minimize work process going to PRIV mode ?
  • What are the SAP parameters used to define initial roll area, extended memory, heap memory, roll area ?
Memory allocation sequence to dialog work processes in SAP :
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  1. Initially , a defined roll area is used. This roll area is defined by the SAP parameter ztta/roll_first.
Usually ztta/roll_first is set to 1 in SAP so that only technically necessary amount  is allocated to roll memory.
 If the memory from the initial roll area( i.e. ztta/roll_first) is not sufficient for the user context then
  1. Extended memory is used until  the extended memory is full or until the user quota is reached
Extended memory is defined by the SAP parameter em/initial_size_MB and the user quota for dialog workprocess is defined by the parameter ztta/roll_extension_dia.
If this memory is also not sufficient, then
  1. The rest of the roll area is used. This roll area is defined by SAP parameter ztta/roll_area.
Once this is also fully occupied then
  1. The system is forced to use local heap memory (Private memory). Then the work process goes into PRIV mode
Heap memory is available until one of the following occurs :
i)        Either the limit of the heap memory for dialog workprocesses is reached (abap/heap_area_dia) or the entire heap memory of all work processes(abap/heap_area_total)  for an application server reaches its limit.
ii)     Operating system limit for allocation of memory
iii)     The swap space in the host system is used up or the upper limit of the operating system address space is reached.

The memory allocation strategy for dialog work processes, aims to prevent work processes from allocating R/3 heap memory and thus entering PRIV mode.
When  a work process enters PRIV mode, it remains connected to the user until the user ends the transaction. Most of the time,  we should try to avoid the situation of work process going into PRIV mode for better performance of the SAP system. This can be done by optimally defining abap/heap_area_total parameter.


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14 comments:

  1. hari11 August 2011 at 20:23

    Hi Brother thanks for your posts, really its very helpful

    Also could you please define Roll Area, Extended Memory and Heap Memory
    Then at what percentages these all memories will be assigned

    Thanks In Advance

    ReplyDelete
    Replies
    1. DurgaPrasad19 June 2013 at 17:10

      Hi Hari...yes will do the same in a separate article

      Delete
  2. DurgaPrasad11 August 2011 at 21:45

    Hi Hari..Thanks a lot for your comment. Definitely will write much more articles on the Memory management covering all the aspects.

    ReplyDelete
  3. kirangadde15 August 2011 at 18:36

    Thanks

    ReplyDelete
  4. DurgaPrasad16 August 2011 at 18:47

    Hi Kiran..Many thanks for your feedback

    ReplyDelete
    Replies
    1. Anonymous2 November 2012 at 18:55

      Hello 'the great'
      you have created really an awesome blogspot wherein i've learned many things, you post so clearly that i got to learn with ease.

      thanks a lot keep booming.....

      Delete
    2. DurgaPrasad19 June 2013 at 17:09

      Thanks dude

      Delete
  5. Unknown17 October 2012 at 22:55

    brother u explained so well , have diagram also it would be better

    ReplyDelete
    Replies
    1. DurgaPrasad19 June 2013 at 17:08

      Hi Satya...Thanks for your suggestion. yes will try to include a diagram.

      Delete
  6. shafeeq19 June 2013 at 12:21

    Awesome Explanation , hats off dude , i like all your posts,
    can i request you to post some docs related to the role of a SAP BASIS Guy in JAVA STAG? ....

    ReplyDelete
    Replies
    1. DurgaPrasad19 June 2013 at 17:08

      Hi Shafeeq...Thanks for your sweet comment...Definitely am looking forward to post more on jack stack administration

      Delete
  7. Unknown13 November 2013 at 18:51

    Hello Durga Prasad,

    The above explanation is so clear that every one can understand.
    Could you please clarify my doubt.

    What is the reason for the difference in memory allocation between dialog and background workprocess in case of unix platform.

    Thanks in advance,
    Raghu.

    ReplyDelete
  8. Anonymous8 April 2015 at 14:22

    What are best values for these parameters which can be set in system. We run background jobs and these jobs often fails due to memory issues. Suppose if I hold data of 2 GB to 4 GB in a background job what values can be set for the memory parameters like 'abap/heap_area_dia'
    'abap/heap_area_nondia'
    'abap/heaplimit'
    'em/initial_size_MB '
    'ztta/roll_area'
    'ztta/roll_extension_dia'
    'ztta/roll_extension_nondia'

    ReplyDelete
  9. Anonymous8 June 2018 at 02:14

    Hi DP this is very helpful for us.

    Thank you

    ReplyDelete

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