SAP Memory Management (an Overview)

SAP Memory ManagementSAP 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

Memory management fundamental :The word memory virtual memory physical main memory + swap space local memory + shared memoryThe 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 processShared memory accessible to multiple operating system process

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 MemoryUser ContextSesions divide into :External sesion opened explicitly by user Internal sesion Opened implicitly by programsubmit, call transaction, call dialog, call screen, call function in update task, call function in background task, and call function starting new task.

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

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

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

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

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

Sequence in which memory is allocated (dialog work process) :

Sequence in which memory is allocated (non-dialog work process) :

SAP EG Memory and SAP Paging Memory Data can be stored globally between user contextSAP 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

SAP Paging MemoryObject 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 calledSUBMIT 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

ServerGlobal Memory (shared memory)Local memoryAdditional local heap memory (if required)LocalmemoryLocalmemoryLocalmemorySAP Roll FileSAP Paging File WorkProcessWorkProcessWorkProcess1 : n1 : 1

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

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 InstanceZero administration memory magement : PHYS_MEMSIZE parameter defines how much of a computers total physical memory should be used for the SAP instance.

Address Space Restriction (Unix)

Address Space Restriction (Windows)

Assistance With TroubleshootingError 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.

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_MEMORYThe Program encounters a memory bottleneck during sorting. EXSORT_NOT_ENOUGH_MEMORYAttemp to create error log fails after a terminated program due to lack of memory. RABAX_CALLING_RABAXThe SAP paging memory is used up SYSTEM_NO_MORE_PAGING, TSV_TNEW_PAGE_ALLOC_FAILEDThe 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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