941735

7/31/2019 941735

http://slidepdf.com/reader/full/941735 1/5

19.01.2008 of 5

Note 941735 - SAP memory management for 64-bit Linux systems

Note Language: English Version: 5 Validity: Valid from 31.01.2007

Summary

SymptomRecommendation for parameterization of 64-bit Linux systems.

More TermsLinux memory management, es/implementation, STD, MAP, TMPFS, /dev/shm,

64-bit, em/initial_size_MB

Cause and PrerequisitesFor SAP on Linux, two different memory management systems are available.

You can switch between the two systems using the SAP instance profile

parameter es/implementation:

o MAP implementation (es/implementation=map)

This variant is mainly used for 32-bit systems, and is described in

detail in Note 386605.

As of SAP kernel 6.20, an SAP system on Linux uses the MAP

implementation by default, in which only the currently active user

context is displayed in the address space of the work process.

o STD implementation (es/implementation=std)

With this variant, the memory management of an SAP system on Linuxis the same as on standard UNIX systems. This means that all user

contexts are displayed in the address space at the same time, which

means that this variant is only available for 64 bit systems.

While the MAP implementation should be used exclusively on 32-bit Linux in

more cases, both variants can be used on 64-bit systems. However, since

there are no longer any 32-bit restrictions, there is no longer any need to

use the special MAP implementation on 64-bit Linux systems .

For this reason, the STD implementation for SAP systems on64-bit Linux is activated by default as of SAP Kernel 7.10.

SolutionIf you want to use the STD implementation with older SAP kernels, you can

activate it using the profile parameter es/implementation=std.

Relevant parameters for the STD implementation

A) SAP profile parameters

o em/initial_size_MB

This parameter specifies how much Extended Memory is available to

the SAP system.

7/31/2019 941735


19.01.2008 of 5


In the SAP Extended Memory, there are additional SAP internal

memory areas, which cannot be directly accessed by the user

contexts. These include the areas that are configured using the

parameters em/global_area_MB and abap/shared_objects_size_MB. Note:

For the user contexts in the system, only the difference of

em/initial_size_MB - (em/global_area_MB +

abap/shared_objects_size_MB)

can be used as Extended Memory.

o ztta/roll_extension

This parameter specifies how much SAP Extended Memory is available

to an individual user context.

This quota can be set differently for dialog and background work

processes if necessary. To do this, use the parametersztta/roll_extension_dia for dialog work processes or

ztta/roll_extension_nondia for background work processes.

The three profile parameters used with the MAP implementation

(em/address_space_MB, em/max_size_MB and PHYS_MEMSIZE) are notrelevant if you use the STD implementation.

B) Linux operating system parametersThe following Linux kernel parameters can be configured using the sysctl

interface. To do this, you must edit the file /etc/sysctl.conf accordingly:

o kernel.shmmax

This kernel parameter specifies how large an individual SysV Shared

Memory Segment is allowed to be. In the case of an STD

implementation, the parameter must be set sufficiently large in

order to allow em/initial_size_MB. The value is specified in the

unit Bytes so that "21474836480", for example, permits segments of

20 GB.

o kernel.shmall

This kernel parameter specifies how much SysV Shared Memory is

available in the Linux system as a whole. As an estimate for therequirements of the SAP system, you can use the total of the SAP

Extended Memory (em/initial_size_MB) + SAP buffer (transaction ST02

-> Detail analysis menu -> Storage, row with the entry "Total").

If several SAP systems are running on a Linux server, the

requirements increase accordingly. The same applies for databases

that may be operating on the same Linux server.

As a configuration recommendation, kernel.shmall can be configured

as the amount of virtual memory in the Linux system (RAM + Swap).

The value is specified in the unit "4 KB blocks", so that"5242880", for example, permits 20 GB SysV Shared Memory in the

Linux system as a whole.

7/31/2019 941735


19.01.2008 of 5


o TMPFS

With the STD implementation, the SAP Extended Memory is no longer

stored in the TMPFS (under /dev/shm). However, the TMPFS is

required by the Virtual Machine Container (VMC). For this reason,

we still recommend the same configuration of the TMPFS:

75% (RAM + Swap) is still recommended as the size.

Points to remember when using the STD implementation

o Background work processes now use memory close to the process

(heap) as the first large memory type. The allocation sequence for

"NonDia" work processes is as follows:

1. Roll memory (ztta/roll_first),

2. Heap memory (abap/heap_area_nondia),

3. Roll memory (ztta/roll_area - ztta/roll_first),

4. Extended Memory (ztta/roll_extension(_nondia)).

In the case of dialog work processes, the allocation sequence

remains unchanged from that used in the MAP implementation:

1. Roll memory (ztta/roll_first),

2. Extended Memory (ztta/roll_extension(_dia)),

3. Roll memory (ztta/roll_area - ztta/roll_first),

4. Heap memory (abap/heap_area_dia).

The allocation sequence can be changed using the RSMEMORY report.

o In transaction ST02, the "In Memory" display for the "Extended

Memory" entry shows the SAP Extended Memory available for the SAP

instance. The value of the parameter em/initial_size_MB is used as

a basic value. However, the Extended Memory is not automatically

increased to the value of em/max_size_MB with the STD

implementation.

Frequent problems in connection with the STD implementationThe following problems or error messages may occur when you carry out the

STD implementation:

o ERROR shmget() (28: No space left on device)

Example from dev_w0:

...

M SHM_ROLL_ADM (addr: 0x2a99dc7000, size: 2672386)

M SHM_PAGING_ADM (addr: 0x2bb1ae6000, size: 656416)I *** ERROR => shmget(13040,112000000,2016) (28: No space left on

device) [shmux.c 1407]

7/31/2019 941735


19.01.2008 of 5


I *** ERROR => shmget(13040,112000000,992) (28: No space left on

device) [shmux.c 1407]

I *** ERROR => Shm Pool Create Error. PoolKey=40, Key=48. [shmux.c

1892]

...

Example from dev_disp:

...

EmInit: MmSetImplementation( 2 ).

MM global diagnostic options set: 0

client 0 initializing ....

InitFreeList

block size is 4096 kByte.

Using implementation std

EsStdUnamFileMapInit: shmget() of 10737418240 bytes failed.

errno = 28(No space left on device)

EsStdInit: unable to allocate 10240 MB

EsStdInit: try to allocate 8192 MB

EsStdUnamFileMapInit: shmget() of 8589934592 bytes failed.errno = 28(No space left on device)


...


EsStdUnamFileMapInit: shmget() of 8388608 bytes failed.

errno = 28(No space left on device)



*** ERROR => EsStdInit: unable to allocate 10240 MB [esuxi.c

401]

*** Error 11 while initializing OS dependent part.

*** ERROR => DpEmInit: EmInit (1) [dpxxdisp.c 9559]

*** ERROR => DpMemInit: DpEmInit (-1) [dpxxdisp.c 9486]

*** DP_FATAL_ERROR => DpSapEnvInit: DpMemInit

*** DISPATCHER EMERGENCY SHUTDOWN ***

...

According to 'man 2 shmget' , the error "No space left on device"

(ENOSPC) signifies that the requested memory exceeds the system

limit for Shared Memory (SHMALL).

Therefore, check the value of the sysctl parameter kernel.shmall

(/proc/sys/kernel/shmall).

o ERROR shmget() (22: Invalid argument)

Example from dev_w0:

...

A Fri Oct 22 16:18:47 2005

A

A ---PXA-------------------------------------------

A PXA INITIALIZATION

A System page size: 4kb, admin_size: 31788kb.

I *** ERROR => shmget(11906,1126400000,2016) (22: Invalid

argument) [shmux.c 1904]

A RABAX in run level 1 A RABAX in unkown environment:

task_type=0, run level=1, rabax state=80000000...

7/31/2019 941735


19.01.2008 of 5


According to 'man 2 shmget', the error "Invalid argument" (EINVAL)

signifies that you try to create a Shared Memory Segment (in this

case the ABAP program buffer (abap/buffersize) that is larger than

permitted by SHMMAX.

Therefore, check the value of the sysctl parameter kernel.shmmax

(/proc/sys/kernel/shmmax).

Header Data

Release Status: Released for CustomerReleased on: 31.01.2007 16:11:56Priority: Recommendations/additional infoCategory: Consulting

Main Component BC-OP-LNX Linux

Valid Releases

Software Component Release FromRelease

To Release and Following

KRNL64NUC 7.00 7.00 7.00 X

KRNL64NUC 6.40 6.40 6.40 X

KRNL64UC 7.00 7.00 7.00 X

KRNL64UC 6.40 6.40 6.40 X

KRNL64UC 7.10 7.10 7.10 X

Related Notes

Number Short Text

958253 SUSE LINUX Enterprise Server 10: Installation notes

923610 Memory param recommendations for Bank Analyzer 4.2 and 5.0

883726 BIA 7.00: Central Note SAP NetWeaver BI accelerator

797084 SUSE LINUX Enterprise Server 9: Installation notes

386605 SAP Memory Management for Linux (32-bit)

171356 SAP software on Linux: Essential information146289 Parameter Recommendations for 64-Bit SAP Kernel

Attributes

Attribute Value

Operating system LINUX

941735

Documents