BC Memory Management
This documentation introduces you to the SAP R/3 Memory Management System and explains
which parameters are available and what the optimal settings for your system are.
It describes the basic functions of the SAP Memory Management System and how best to
configure your system depending on the platform you use, the available resources, and what you
want your system to do.
It also describes hardware and operating system requirements and explains how to monitor the
system and recognize and resolve problems.
Contents
BC Memory Management ..............................7
Functions of the R/3 Memory Management System ....................8
R/3 Memory Types............................................................................. 10
R/3 Roll Area ....................................................................................... 11
R/3 Extended Memory......................................................................... 12
Private Memory ....................................................................................13
Platform-Specific Description of Memory Management............... 15
Memory Management under UNIX ................................................... 16
Implementing Memory Management (UNIX).................................. 18
Allocating Memory for User Contexts (UNIX) ..................................19
Implementing the Extended Memory Under UNIX.......................... 23
Configuration for UNIX ........................................................................ 24
Configuration for AIX ............................................................................ 26
Setting the Profile Parameters (UNIX) ................................................ 28
Sample Configurations (UNIX)............................................................... 31
Application Servers with Up to 15 Users (UNIX) ............................... 32
Application Servers with Up to 50 Users (UNIX) ................................ 34
Application Server with Over 50 Users (UNIX) ......................................36
Operating System and Hardware Requirements (UNIX) ................... 39
Data Segment Size (UNIX) ........................................................................... 40
VPAGEMAX under OSF/1................................................................................. 41
Shared Memory ID under IBM AIX...................................................................................... 42
Checking the Hardware and Operating System of the Host System (UNIX)...................... 43
Documentation not Available in Release 4.6B ......................................................................... 44
Documentation not Available in Release 4.6B.................................................................... 45
Windows NT ................................................................................................................................ 46
Implementation on Windows NT .............................................................................................. 47
Implementing the Extended Memory Under Windows NT .................................................. 48
Special Features under Windows NT....................................................................................... 50
Rules for Memory Management under Windows NT ............................................................... 51
Minimizing the Windows NT File Cache.............................................................................. 52
Maximum Use of Extended Memory................................................................................... 53
Setting Dimensions for Sufficient Extended Memory.......................................................... 54
Determining the Number of Work Processes...................................................................... 55
Parameter Overview for Windows NT................................................................................. 56
Memory Management on AS/400 ............................................................................................... 57
Storage Pool Requirements (AS/400) ...................................................................................... 59
Checking the Hardware and Operating System of the Host System.................................. 60
Extended Memory with Teraspace Shared Memory Segments (AS/400) ............................... 61
Configuration for AS/400 .......................................................................................................... 63
Temporary Storage (AS/400) .............................................................................................. 65
Setting the Profile Parameters (AS/400) ............................................................................. 66
Sample Configuration (AS/400) .......................................................................................... 69
Application Server with up to 15 Users (AS/400)........................................................... 70
Application Server with up to 50 Users (AS/400)........................................................... 73
Application Server with over 50 Users (AS/400)............................................................ 76
Operating System and Hardware Prerequisites (AS/400)........................................................ 79
Profile Parameters of Memory Management............................................................................. 80
abap/heaplimit: Work Process Restart...................................................................................... 82
ztta/roll_extension: Extended Memory Limit ............................................................................ 84
abap/heap_area_dia: Heap Memory Limit for Dialog Work Processes.................................. 86
abap/heap_area_nondia: Heap Memory Limit for Non-Dialog Work Processes................... 87
abap/heap_area_total: Heap Memory Limit .............................................................................. 88
em/initial_size_MB: Extended Memory Pool Size .................................................................... 89
rdisp/ROLL_SHM: Roll Buffer Size ............................................................................................ 90
rdisp/ROLL_MAXFS: Maximum Roll File Size .......................................................................... 91
rdisp/PG_SHM: Paging Buffer Size............................................................................................ 92
rdisp/PG_MAXFS: Maximum Size of the R/3 Paging File ........................................................ 93
ztta/roll_first: Initial Allocation Size from the Roll Area .......................................................... 94
ztta/roll_area: Roll Area............................................................................................................... 95
em/blocksize_KB: Segment Size of the Extended Memory .................................................... 97
em/stat_log_size_MB: Statistics - User Context Size .............................................................. 98
em/stat_log_timeout: Statistics - User Context Size ............................................................... 99
Monitoring the Memory Management System........................................................................ 100
Checking Roll /Paging Area and Extended Memory using Transaction ST02 .................... 101
Monitoring Memory Resources Using Transaction ST06...................................................... 102
Swap Space Requirements....................................................................................................... 104
Documentation not Available in Release 4.6B........................................................................ 106
Monitoring on UNIX ................................................................................................................... 107
Determining the Swap Space Currently Available (UNIX) ..................................................... 108
Determining Swap Space Requirements (UNIX) ................................................................... 109
Checking Page Fault Rates (UNIX)........................................................................................ 110
Monitoring on Windows NT ...................................................................................................... 113
Windows NT: Checking Page Fault Rates ............................................................................. 114
Checking Unused Working Memory Using Transaction ST06 (Windows NT) ....................... 115
Monitoring on AS/400................................................................................................................ 116
Increasing the Size of Main Storage Pools (AS/400) ............................................................. 117
Checking Page Fault Rates (AS/400) .................................................................................... 118
Recognizing and Correcting Problems ................................................................................... 120
Swap Space Bottleneck During R/3 Operation....................................................................... 121
Slow Response Times for certain Users, Very Good Response Times for other Users.... 122
Platform-Specific Problems (UNIX).......................................................................................... 125
Preventing Swap-Space Bottlenecks (UNIX) ......................................................................... 126
OSF/1 from DEC: Memory Allocation Problems .................................................................... 127
IBM AIX: Background Processing Problems due to Segment Size Limitations..................... 128
IBM AIX: Start or Enqueue Problems or No Connection to Programs SAPOSCOL.............. 129
Platform-specific Problems: Windows NT ...................................................................... 130
Platform-Specific Problems (AS/400) ...............................................131
Terminology ............................................................................... 132
Work Process........................................................................... 133
Virtual Address Space of a Work Process..................................134
SAP Paging ........................................................................... 135
User Context ..........................................................................136
R/3 Session ...........................................................................138
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