SAP Basis Online Trainings
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
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
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.
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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
èShared 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
è- Shared memory which mostly of user context stored
è - All SAP work process can edit stored user context directly
è - Roll in rather only copied the address (pointer) of where a user context located on the SAP extended memory.
è- makes roll process much faster
SAP Extended Memory main parameters :
è em/initial_size_MB : size of SAP extended memory allocated when the SAP instance starts up
è em/blocksize_KB : size block which split SAP Extended Memory
è ztta/roll_extension : maximum size of a user context in the SAP Extended memory
SAP Heap Memory
è Area which allocated variably as local memory as required.
è Released after a transaction is complete.
SAP Extended Global Memory
è Used to store data across user context
è Allows fast & copy-free switching based on mapping.
è Substracted from SAP Extended Memory to calculate the remaining
storage space
è configured using em/global_area_MB parameters
SAP Heap Memory main parameters :
è abap/heap_area_dia : quotas oh SAP heap memory that a dialog process can allocated.
è abap/heap_area_nondia : quotas oh SAP heap memory that a nondialog process can allocated.
è abap/heap_area_total : size that can be allocated in total by all work process.
è abap/heaplimit : Workprocess restart limit of heap memory