memorymanagement sap nw
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7/25/2019 Memorymanagement SAP NW
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SAP Memory Management
(an Overview)
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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
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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
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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
User Context
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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Pres.
server SAP Application Sever DB Server
S A P
G U I SAP Extended Memory
DispatcherQueue SAP Roll Memory
d i s p a t c h e r
Table
buffer
Program
buffer
DDICBuffer
Work Process
Work Process
Work Process
DB Process
DB Process
DB Process
Database
buffer
Process Flow
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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
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
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Roll file
Roll
(local)
Roll Buffer (shared)
Roll In /
Roll Out
rdisp/roll_SHM
rdisp/roll_MAXFS
ztta/roll_first
ztta/roll_area
Roll buffer (shared memory)
Roll area
(local)
Roll file (disk)
Roll area
(local)
Work
Process1
Work
Process2
copy copy
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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
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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
ztta/roll_extension
em/initial_size_MB
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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
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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 nondialogprocess 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
Heap
Memory
(local)
abap/heap_area_(non)dia
abap/heap_area_total
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Sequence in which memory is allocated (dialog work process) :
User-
IndependentData Roll memory to
zttz/roll_first
Roll memory to
zttz/roll_extension
Roll memory to
zttz/roll_area
Roll memory to
abap/heap_area_dia
1 2 3 4
User Context
Copying data
during contextchange
Mapping the data duringcontext change
- Data stays in work process
- No context switch possible
- Work process in private mode
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User-
Independent
Data Roll memory to
zttz/roll_extension
Roll memory to
zttz/roll_area
Roll memory to
abap/heap_area_dia
1 2 3
User Context
Copying dataduring context
change
Mapping the 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) :
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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 remainingstorage space
configured using em/global_area_MB parameters
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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, CAL L TRANSACTION, CAL L DIALOG, CALL SCREEN,
CALL FUNCTION IN UPDATE TASK , CAL L 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
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SAP paging
buffer
SAP buffers
(contains e.g SAP Programs)
Extended Memory
(User Context)
Server
SAP roll buffer
Global Memory (shared memory) Local memory
Additional local
heap memory (if required)
Local
memory
Local
memory
Local
memory
SAP Roll File
SAP Paging FileWork
Process
Work
Process
Work
Process
1 : n 1 : 1
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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
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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.
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User Independent
WP
Local
SAP
Buffers
(Shared)
User Context
Roll
Memory
(Shared)
SAP Extended Memory
(Shared)
SAP Heap Memory
(local)
em/address_space_MB abap/heap_area_(non_)dia
Address Space
SAP Work
Process
SAP Extended Memory Total
em/initial_size_MB
Address Space Restriction (Windows)
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Assistance With Troubleshooting
Error because of incorect memory area configuration :
Operating System can not start because the operating systemcannot 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.
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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