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SAP Memory Management (an Overview)

SAP Memory Management (an Overview)

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SAP Memory Management (an Overview)

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  1. SAP Memory Management (an Overview)

  2. SAP Memory Management • SAP Memory areas overview : • SAP Buffer • SAP Roll Memory • SAP Extended Memory • SAP Heap Memory • SAP Paging Memory • Fixed Local Memory of the SAP work Process • Main factors in configuring SAP Memory : • Physical Main Memory (RAM) •  give attention to ratio between physical and virtual memory • Operating system options and restrictions •  compare between 32 and 64 bit system architecture

  3. Memory management fundamental : The word “memory”  virtual memory  physical main memory + swap space  local memory + shared memory • The maximum amount of virtual memory that can be allocated is limited by two variable : • Result of physical hardware restriction • Maximum address space permited by operating system • The Operating System manages two type of memory : • Local memory •  allocated precisely to one operating system process • Shared memory •  accessible to multiple operating system process

  4. User Context • Reffered : • Data which is generated by transaction process • Variables, Internal table & screen list • New sesion = new user context • Data is stored independently in different memory areas • Stored in SAP roll memory, SAP extended memory, & SAP Heap Memory • Sesions divide into : • External sesion  opened explicitly by user • Internal sesion  Opened implicitly by program submit, call transaction, call dialog, call screen, call function in update task, call function in background task, and call function starting new task.

  5. Process Flow Pres. server SAP Application Sever DB Server Table buffer Program buffer SAP Extended Memory Database buffer SAP GUI DDIC Buffer Dispatcher Queue SAP Roll Memory Work Process DB Process dispatcher Work Process DB Process Work Process DB Process

  6. SAP Roll Memory • Local SAP Roll area of work process - The initial part of user context stored - Each SAP work process can only access its own roll area • Shared SAP Roll Area - Accessible to all of instance work processes - Buffer to temporary keep user context when a user is assigned to new work process • Roll in : copying user context from shared roll area to local roll area • Roll Out : copying user context from local roll area to shared roll area

  7. Roll buffer (shared memory) Roll area (local) Roll area (local) Work Process2 Work Process1 Roll file (disk) rdisp/roll_SHM Roll Buffer (shared) ztta/roll_first Roll (local) Roll In / Roll Out copy copy ztta/roll_area Roll file rdisp/roll_MAXFS

  8. SAP Roll area parameters • - ztta/roll_first : First amount of roll area used in a dialog WP • - ztta/roll_area : size of the local SAP Roll area in the work process • rdisp/ROLL_SHM : size of SAP roll Buffer • rdisp/ROLL_MAXFS : size of entire shared SAP roll area

  9. em/initial_size_MB ztta/roll_extension • SAP Extended Memory • Shared memory which mostly of user context stored • All SAP work process can edit stored user context directly • Roll in rather only copied the address (pointer) of where a user context located on the SAP extended memory. • makes roll process much faster

  10. SAP Extended Memory main parameters : • em/initial_size_MB : size of SAP extended memory allocated when the SAP instance starts up • em/blocksize_KB : size block which split SAP Extended Memory • ztta/roll_extension : maximum size of a user context in the SAP Extended memory

  11. abap/heap_area_(non)dia Heap Memory (local) abap/heap_area_total • SAP Heap Memory • Area which allocated variably as local memory as required. • Released after a transaction is complete. • SAP Heap Memory main parameters : • abap/heap_area_dia : quotas oh SAP heap memory that a dialog process can allocated. • abap/heap_area_nondia : quotas oh SAP heap memory that a nondialog process can allocated. • abap/heap_area_total : size that can be allocated in total by all work process. • abap/heaplimit : Workprocess restart limit of heap memory

  12. User Context 1 2 3 4 User-Independent Data Roll memory to zttz/roll_first Roll memory to zttz/roll_area Roll memory to abap/heap_area_dia Roll memory to zttz/roll_extension Copying data during context change • Data stays in work process • No context switch possible • Work process in private mode Mapping the data during context change Sequence in which memory is allocated (dialog work process) :

  13. User Context 1 2 3 User-Independent Data Roll memory to zttz/roll_area Roll memory to abap/heap_area_dia Roll memory to zttz/roll_extension Mapping the data during context change Copying data during context change • Data stays in work process • No context switch possible • Work process in private mode Sequence in which memory is allocated (non-dialog work process) :

  14. SAP EG Memory and SAP Paging Memory  Data can be stored globally between user context • SAP Extended Global Memory • Used to store data across user context • Allows fast & copy-free switching based on mapping. • Substracted from SAP Extended Memory to calculate the remaining storage space • configured using em/global_area_MB parameters

  15. SAP Paging Memory • Object that stored in the SAP Paging Memory : • ABAP data cluster stored temporarily with ABAP statement IMPORT/EXPORT FROM/TO MEMORY • Parameter transferred when programs and transaction called SUBMIT REPORT, CALL TRANSACTION, CALL DIALOG, CALL SCREEN, CALL FUNCTION IN UPDATE TASK, CALL FUNCTION BACKGROUND TASK, CALL FUNCTION STARTING NEW TASK  Data extracts created by statement EXTRACT (up to basis 4.5) • SAP Paging Memory Main Parameters : • rdisp/PG_MAXFS : Size of SAP Paging Memory • rdisp/PG_SHM : Size of SAP Paging Buffer (shared memory) • Error caused by SAP Paging Memory : • TSV_TNEW_PG_CREATE_FAILED • SYSTEM_NO_MORE_PAGING

  16. SAP buffers (contains e.g SAP Programs) SAP roll buffer SAP paging buffer Extended Memory (User Context) Server Global Memory (shared memory) Local memory Additional local heap memory (if required) Local memory Local memory Local memory 1 : 1 1 : n SAP Roll File Work Process Work Process Work Process SAP Paging File

  17. Configuring & Monitoring SAP Memory Areas Main Objective :  Performance  Stability • Main Factors to be considered : • Physical Main Memory (RAM) • Swap space or paging file of the operating system • Operating system restriction

  18. Next points to be considered : • Total Main Memory Requirement • Number of Computer • Several SAP instances per computer • SAP extended memory and roll buffer • Memory for SAP work process • Database Instance • Zero administration memory magement : • PHYS_MEMSIZE parameter defines how much of a computer’s total physical memory should be used for the SAP instance.

  19. abap/heap_area_(non_)dia em/initial_size_MB User Context User Independent SAP Buffers (Shared) Roll Memory (Shared) SAP Extended Memory (Shared) SAP Heap Memory (local) WP Local Address Space SAP Work Process Address Space Restriction (Unix)

  20. em/initial_size_MB SAP Extended Memory Total abap/heap_area_(non_)dia em/address_space_MB User Context User Independent SAP Buffers (Shared) Roll Memory (Shared) SAP Extended Memory (Shared) SAP Heap Memory (local) WP Local Address Space SAP Work Process Address Space Restriction (Windows)

  21. Assistance With Troubleshooting • Error because of incorect memory area configuration : • Operating System can not start because the operating system cannot provide the requsted memory area • Session terminations  User is logged off • ABAP Program termination. • Four error factors : • Program errors (e.g endless loop) • SAP Profile parameters are set incorectly • The Swap Space on the operating system is not large enough • Configuration parameters of the operating system are set incorectly or OS limits have been reached.

  22. ABAP Program Termination : • The memory of user context is used up : STORAGE_PARAMETERS_WRONG_SET, SYSTEM_ROLL_IN_ERROR, TSV_TNEW_BLOCKS_NO_ROLL_MEMORY, TSV_TNEW_PAGE_PAGE_ALLOC_FAILED, TSV_TNEW_INDEX_NO_ROLL_MEMORY • System can not create the program buffer because there is not not sufficient shared memory at that time PXA_NO_SHARED_MEMORY • The Program encounters a memory bottleneck during an operation in the database interface DBIF_RTAB_NO_MEMORY, DBIF_RSQL_NO_MEMORY • The Program encounters a memory bottleneck during sorting. EXSORT_NOT_ENOUGH_MEMORY • Attemp to create error log fails after a terminated program due to lack of memory. RABAX_CALLING_RABAX • The SAP paging memory is used up SYSTEM_NO_MORE_PAGING, TSV_TNEW_PAGE_ALLOC_FAILED • The memory for SET/GET parameter (SPA/GPA memory) is used up. SET_PARAMETER_MEMORY_OVERFLOW • Volume limit of memoy allocated to single call (ztta/max_memreq_MB) is set too low SYSTEM_NO_ROLL

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