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As discussed in Query Performance and Memory Consumption, a BW query uses extended and heap memory. SAP extended memory is the core of the SAP memory management system. Each SAP work process has a part reserved in its virtual address space for extended memory. The parameter ztta/roll_extension specifies how much extended memory can be allocated from the pool to one user context. If the pool is used up, heap memory is allocated. The work process switches to the PRIV mode and is reserved exclusively for the current user context. Hence the most important parameters regarding query execution are abap/heap_area_dia and ztta/roll_extension(or ztta/roll_extension_dia - see note 715277).  

You can check how much memory a single query can allocate(maximum) in transaction ST02 → button 'Detail Analysis Menu' → button SAP 'Memory'

So, in total a query on this system cannot allocate more than about 6GB Memory.

If you want to check the memory parameters on your system, you can run the transaction ST02 and then click on the button 'Current Parameters'. In this context the most important parameters are:

  • em/initial_size_MB: the total size specified here for the EM should be large enough to contain the total of all user contexts
  • ztta/roll_extension: You can restrict the maximum usage of an individual user with this parameter. This prevents one single user from using up the entire extended memory. If the maximum allowed EM memory for a dialog user is used up, heap memory is allocated.
  • abap/heap_area_dia: This value specifies how much PRIV memory can be allocated for a user context by a single dialog work process. In this way you can ensure that a single user cannot use the entire available PRIV memory ( abap/heap_area_total).

In case a certain query exceeds these limits, you need to check whether it is possible to increase these parameters(if not, then the query has to be restricted, see Query Performance and Memory Consumption). Please ask your basis administrator for help. Check also the online documentation(link below) for further details.

SAP Online Documentation

Profile Paramters of Memory Management

SAP Notes

  • 2085980 New features in memory management as of Kernel Release 7.40
  • 715277   New instance profile parameters

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