Basis and others: Note 146528 - Configuration of R/3 on hosts with much RAM

Summary

Symptom
You want to configure an R/3 System on a computer with a lot of RAM (more than 2 GByte RAM). The 32-bit architecture used so far involves several restrictions so that the existing main memory often cannot be managed efficiently.
Other terms
Performance, 64-bit, 64 bit, SHMEM_MAGIC, memory windowing
Reason and Prerequisites
This note applies to UNIX operating systems only.
Solution

I. General remarks

1. R/3 kernel release: We basically recommend to use the newest R/3 kernel patch level. This is in particular the case if you are using one of the special solutions described in this note.

2. Swap space: For the special solutions described here a large swap space is required. We recommend a swap space size of 3 to 4 times the RAM size, even though a swap space of 10 GByte or more might have to be created.

3. Shared memory and local memory                        The virtual memory which is available for a process is divided into "shared memory" and "local memory". The shared memory can be accessed by all processes of an instance, the local memory can only be accessed by one process.
                       Most of the memory used in the R/3 environment is shared memory. Experience has shown that the memory used is divided into 80% shared memory and 20% local memory. (In individual cases, there might of course be exceptions to this rule). Shared memory restrictions by the operating system therefore affect the configuration options of the R/3 System drastically.
                       The shared memory includes:
           - All R/3 buffers (program buffers, table buffers,
  Roll buffers and so on)
- The R/3 extended memory
                       The local memory includes:
                       - Local memory of the work processes (heap)

4. 32-bit and 64-bit technology                        In the 32-bit technology used so far, it is theoretically possible to address a maximum of 4 GByte of memory from one process. Since a lot of memory can actually not be used at all due to fragmentation effects, the memory which is actually available for an R/3 work process is much smaller in practice. In the following sections, the restrictions are specified for some operating systems.
                       With the 64-bit technology these problems are solved. Here, an address space of many Terabytes is available for a work process. To be able to use the 64-bit technology you need a 64-bit operating system, a 64-bit version of the database software and a 64-bit version of the R/3 kernel.
                       Compared to the 32-bit version, the 64-bit R/3 kernel has no new functions. Compared to the 32-bit using the 64-bit version remains the same for users and adminstrators.
                       The memory management gets considerably simpler when you use the 64-bit kernel as compared to the 32-bit version. Details can be found in Note 146289.

                       The following 64-bit products are currently released:

b) R/3 kernel:

R/3 Release 4.0 and higher: See also under the different operating systems
A 64 bit version of the R/3 kernel for R/3 Release 3.0/3.1 is not planned.

c) Information on released 64 bits products can be found in R/3 notes of component XX-SER-SWREL or in the SAP Marketplace under http://service.sap.com/platforms

NOTE: If you want to use 64 bits databases or 64 bit R/3, you must at least provide a development or test system which you also change to 64 bit technology. All Uprades of operating system, database or the use of a new R/3 kernel must always be carried out in a development or test system before productive use. (this is not specifically applies to using the 64 bit kernel but should be precondition for all changes to the system.)

II. Compaq Tru64 UNIX (OSF/1, Digital UNIX)

1. Availability of the R/3 64-bit kernel For OSF/1, R/3 is delivered with a 64-bit kernel.
Also see: R/3 Notes 32915, 25960, 97179

2. Several R/3 instances on one server Several instances can be configured at the same time. The corresponding restrictions apply to one instance each.
Also see: R/3 Note 21960

III. SOLARIS

1. Availability of the R/3 64-bit kernel A 64-bit kernel is available for R/3 Release 4.6 (kernel release 4.6D) in conjunction with SOLARIS 7 and 8 (both 8-bit systems) and Oracle (64-bit). For more details, please refer to Note 353110 and under http://service.sap.com/platforms.

2. Standard installation:

a) For a standard R/3 System installation on SOLARIS for each R/3 instance (precisely: for each work process) about 3500 MByte of address space available. The total of Shared memory (= R/3 Extended memory, all buffers) and local memory (parameter abap/heap_area_dia or abap/heap_area_nondia) must therefore be smaller than 3500 MByte. See also Note 97497.

3. Several R/3 instances on one server Several instances can be configured at the same time. The corresponding restrictions apply to one instance each.
Also see: R/3 Note 21960

IV. AIX

1. Availability of the R/3 64-bit kernel A 64-bit kernel for AIX 4.3.x (x >= 2) and R/3 Release 4.0 and higher is currently available. Details can be found under:
http://service.sap.com/platforms

2. Operating system version and patch level You need to use at least AIX version 4.2.1 to apply the information of this note. You find the required patch level for AIX and the R/3 in Note 143646.

3. 32-bit Standard installation:

a) For an R/3 standard installation on AIX, 11 segments of 256 MByte each are available as shared memory.

b) R/3 buffers must therefore be grouped together in so-called pools which must not be bigger than 256 MByte each. That means, in general you can only create R/3 buffers with a maximum size of 256 MByte. Pool 40 is an exception, it can be created via 2 AIX segments that is with a size of 512 MByte. Details on the pool settings can be found in Note 98084. We recommend to group all R/3 buffers in pools 10 (with a size of a maximum of 265 MByte) and 40 (with a size of a maximum of 512 MByte). As a consequence 768 MByte are available for the R/3 buffers. This size suffices in most cases.

c) The R/3 Extended Memory is created across several AIX segments. In order not to waste any address space we recommend that you configure the R/3 extended memory in steps of 256 MByte, that is 256 (= 1 AIX segment), 512, 768, 1024 or 1280 MByte. (As an alternative you can also round in 250-MByte steps, that is, 250, 500, 750, 1000 or 1250 MByte.)

4. Alternative memory management (32-bit R/3 kernel) To be able to use the memory of a computer with 2 GByte and more efficiently, you allocate an R/3 extended memory of more than 1250 MBytes if required. In this case we recommend that you use the so-called "Alternative memory management on AIX". Possible scenarios can be found in Notes 95454 and 124555.

5. Shared memory segments larger than 256 MByte for AIX 4.3.1                        With AIX 4.3.1 it is theoretically possible to create any shared memory segments with a size of more than 256 MByte (see R/3 Note 117267). If you want to do this, a lot of address space is wasted through fragmentation effects so that in the end you can allocate less memory. If you want to use this possibility we recommend to adjust the size of the respective segments to a multiple of 256MB or little less but not little more.
                       For example Pool 10: 510MB, 512MB, 768MB, but not 260MB or 600MB
                       For example Pool 40: 768MB, 1024MB, but not 600MB or 800MB
                       The same is true for further Shared Memories with more than 256MB if they are not in a Pool.
                       For example Program buffer: 500MB, 512MB, 768MB, but not 300MB or 800MB

6. Several R/3 instances on one server Several instances can be configured at the same time. The corresponding restrictions apply to one instance each.
Also see: R/3 Note 21960

V. HP-UX

1. Availability of the R/3 64-bit kernel A 64-bit kernel is currently available for HP-UX >= 11.0 and R/3 Release >= 4.0. Detailed information can be found under
http://service.sap.com/platforms and in Notes 146218, 146248, 146289, 155135, 155355.

2. 32-bit Standard installation: With a standard R/3 System installation on HP-UX (32-bit R/3 kernel without SHMEM_MAGIC and without HP memory windowing) a maximum of 1750 MBytes shared memory is available on the entire server. Thus, approximately 2 GByte RAM can be used effectively with a standard installation.

3. SHMEM_MAGIC kernel SAP provides a special kernel (SHMEM_MAGIC kernel) which allows the use of shared memory with a size of 2.75 GByte (see R/3 Note 106819).

4. Memory windowing HP provides a special procedure to generate several memory windows. Each database and each R/3 instance then runs in one memory window. Thus, each database and each R/3 instance is restricted to the size of the shared memory but the shared memory for each computer is not restricted.
The standard memory windowing provides several memory windows with 1 GByte each for the shared memory plus a global window with 0.75 GByte.

5. Combination SHMEM_MAGIC kernel and memory windowing You can use a combination of SHMEM_MAGIC kernel and memory windowing. In this case N memory windows of 2 GByte plus a global window with 0.75 GByte are available
NOTE: Up to now SAP has no experience with productive customers who are using this solution. Therefore such a solution must in any case be tested on a test system.

6. Several R/3 instances                        In the case of several R/3 instances or one R/3 instance and one database, the individual instances and databases must share the available shared memory. For a standard installation it is therefore not recommended that you configure several productive R/3 instances on one computer (exception: small development or test systems).

CAUTION: The installation of the SHMEM_MAGIC kernel or memory windowing must be carried out by an HP consultant. If problems occur during the installation or operation of the SHMEM_MAGIC kernel, there is not a support by the SAP TCC as part of the GoingLive or EarlyWatch check.

7. Summary: Solution Roadmap for HP-UX

a) Does the server have 2 GByte RAM or less?

In this case, the standard installation is generally sufficient.
Note: Only in case of memory bottlenecks during the standard installation you should consider using the 64-bit R/3 kernel or SHMEM_MAGIC or HP memory windowing.

b) Solution for a pure application server (= server with R/3 instance(s), but without database)

(1) R/3 Release 4.0B and higher:
A 64-bit R/3 kernel released in production systems exists. In this case, you can manage as much RAM as you like. You can configure several R/3 instances. The 64-bit kernel is fully supported by SAP (support, GoingLive, EarlyWatch). Provided that a 64-bit kernel is released for an R/3 Release, you have to use this instead of solutions with SHMEM_MAGIC kernels and memory windowing.
(2) R/3-Release 3.0/3.1 NO 64 bit R/3 kernel exists.
If required (that is if the R/3 Extended Memory is completely exhausted and work processes go frequently into the PRIV mode) HP memory windowing or the SHMEM_MAGIC kernel can be used.
If you want to configure several R/3 instances on one application server, use a combination of SHMEM_MAGIC kernel and memory windowing. In this case 2 GByte shared memory for each R/3 instance are available. (Memory Windowing without SHMEM_MAGIC kernel with 1 GByte for each R/3 instance is not recommended since then there is not enough memory available for the R/3 extended memory.)

c) Solution for a database server (= server with database and (possibly) with R/3 instance(s)

           (1) Does an R/3 64-bit kernel released for production systems and a 64-bit version of the database software exist?
In this case, you can manage as much RAM as you like. You can configure several R/3 instances. The 64-bit kernel is fully supported by SAP (support, GoingLive, EarlyWatch). Provided that a 64-bit kernel is released for an R/3 Release, use this rather than solutions with SHMEM_MAGIC kernels and memory windowing.
           (2) Does a 64-bit version of the database software exist but no R/3 64-bit kernel ?
In this case, you can manage as much RAM as you like for the database. For the R/3 instance(s) (with 32-bit R/3 kernel) 1.75 GByte shared memory is available. Depending on the size of the database you can effectively manage RAM up to a size of approximately 4 GBytes. Provided that a 64-bit version of the database software is released, use this rather than the solutions with SHMEM_MAGIC kernel and memory windowing.
           (3) Special solution for INFORMIX databases
For INFORMIX, a compiled version with the SHMEM_MAGIC option exists (see Note 76862). If you use this solution a total of 2.75 GByte shared memory can be allocated.
If you use this solution, we recommend that you use the computer as a pure database server, that is, without R/3 instance.
           (4) Database server with 4 GBytes or more and R/3 Release without 64-bit kernel
If you want to configure several R/3 instances along with the database on one database server, use a combination of SHMEM_MAGIC kernel and memory windowing. In this case 2 GByte shared memory for each R/3 instance is available. (Memory windowing without SHMEM_MAGIC kernel with 1 GByte for each R/3 instance is not recommended.)

Notes:

d) The operation of an application server with more than 2 GByte RAM or a database server with 4 GByte and more always leads to increased administration work. Discuss the appropriate configuration for computers with your HP partner before purchasing them.

e) If you use an SAP GoingLive check or an SAP EarlyWatch check, you need the SHMEM_MAGIC kernel or HP memory windowing already installed, provided that you and your hardware partner decided to use one of these solutions.

f) Configuration of the HP memory windowing cannot be checked by SAP remote (especially in an EarlyWatch or GoingLive check). The recommendations of SAP therefore basically presuppose that the HP memory windowing was installed and configured by a HP consultant in accordance with the HP guidelines for memory windowing. There is no support on SAP side for problems with HP memory windowing. If problems with storage management occur, please contact your HP support.

VI.ReliantUNIX (SINIX)

1. Availability of the R/3 64-bit kernel A 64-bit kernel for RELIANT/SINIX (as of Release 5.44) and R/3 Releases 4.0B and higher are currently available. Detailed information can be found under http://service.sap.com/platforms and in Notes 158709 and 174089.

2. 32-bit Standard installation: With an R/3 standard installation on RELIANT/SINIX, a maximum of about 1600 MByte shared memory for each R/3 instance are available.

3. Several R/3 instances Several instances can be configured at the same time. The 1600 MByte restriction applies to one instance each. Provided that an R/3 instance and a database are configured on one server, you can allocate 1600 MByte for the R/3 instance and 1600 MByte for the database.
See also: R/3 Note 21960

Header Data


Release Status:	Released for Customer
Released on:	12.02.2003 10:07:36
Master Language:	German
Priority:	Recommendations/additional info
Category:	Consulting
Primary Component:	SV-BO Backoffice Service Delivery

Affected Releases

Release-Independent

Related Notes

Note 146528 - Configuration of R/3 on hosts with much RAM

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