FAQ: Memory Management in SAP for Windows

[Former Member]

I would just like to seek insights with regards to the Memory Management in SAP for Windows operating system. What are the logic behind Extended Memory, Shared Memory, Physical Memory and all the SAP Buffers (found in ST02)? What are the relationship behind these memory concepts? Please feel free to provide your insights so as to come up with an FAQ concerning Memory Management in SAP for windows.

[Former Member · Accepted solution]

Hi,

if is better to use 64 bit platform on windows as per SAP recommended

in windows you can use zero memory management.

check sap Note 88416 - Zero administration memory management as of 4.0A/ Windows

103747 - Performance: Parameter recommendations as of Release 4.0

regards,

kaushal

[Former Member]

I see. Thanks for the reminder.

Actually, i have read multiple information from multiple resources. On that note, i have accumulated theoretical information that i need in order to research on things especially those that i didn't fully understand. Having said that, i would like to accumulate the other side of information, the one that is not taught by theories, etc. I am referring to the information that is being brought upon by experience and encounters from SAP Professionals. In this way, perspective and insights that cannot be found from any resources can be viewed via this forum that can be used as reference of everyone. That is the reason why I put it as "it would be appreciated" thus not to limit if one will do redirection to other sources.

[former_member185954]

Hello Jett,

the truth is nobody can predict/judge/determine how your system will behave.

If there is a problem , then we can go around looking for a solution.

If its just resources you are looking for , then i suggest you go around looking in the theoratic documents and links and try to accumulate what you need.

Regards,

Siddhesh

[Former Member]

I would like to seek your perceptions and ideas concerning the relationship between Extended Memory, user context, paging and shared memory. Initially, what are these concepts? What are their function? Basically, what do they do? You could provide scenarios to easily understand and analogize their necessity and function.

[markus_doehr2]

> I would like to seek your perceptions and ideas concerning the relationship between Extended Memory, user context, paging and shared memory. Initially, what are these concepts? What are their function? Basically, what do they do? You could provide scenarios to easily understand and analogize their necessity and function.

Memory management in an operating system is implementation dependent. Each operating system has its own "view" of it. If you search for notes in BC-CST-MM you will find quite a few notes/hints, which OS uses what kind of implementation.

Memory management is not SAP specific but OS specific, if you want to get into those concepts, I suggest a VERY good book:

http://www.amazon.com/Modern-Operating-Systems-3rd-GOAL/dp/0136006639/ref=pd_bbs_sr_2?ie=UTF8&s=book...

For the Windows specific implementations I suggest the boot at

http://www.microsoft.com/technet/prodtechnol/windows2000serv/reskit/iisbook/c05_memory_management.ms...

and

http://technet2.microsoft.com/windowsserver/en/library/74d58697-970a-45db-9139-ebcd3db051181033.mspx...

Explaining here something about full could be written is, in my opinion, beyond the scope of this forum.

Markus

[former_member185954]

Hello Markus,

My god.. i haven't heard the name tanenbaum since 7 years ! that book must be awesome.

i read the one which talks about Amoeba OS etc.. during my computer engineering..

Regards,

Siddhesh

[markus_doehr2]

> My god.. i haven't heard the name tanenbaum since 7 years ! that book must be awesome.

It definitely is - really worth every $ (or €)

> i read the one which talks about Amoeba OS etc.. during my computer engineering..

Maybe we should ask SAP to port to Amoeba?

http://www.cs.vu.nl/pub/amoeba/

Markus

[former_member185954]

i meant in the past tense the book (orange coloured) is somewhere in my old closet in my house.

[markus_doehr2]

> i meant in the past tense the book (orange coloured) is somewhere in my old closet in my house

Does it mean, you rarely visit that "throne" or is this place a sign of your appreciation for the author?

Markus

[former_member185954]

ah...

nope.. i once fantasised about writing my own OS kernel on GNU C .. so i had got that book .. after that graduating i left my home within a year and haven't returned for a long time now , hopping in different cities so never got a chance to open that book again.

the author is terrific indeed infact legendry might be the word.. and i think there are two tanenbaums one who wrote the OS book and the other who wrote book on Computer networks.

i have read both .. anyways this thread is about memory management. and we are discussing something else

Regards,

Siddhesh

[markus_doehr2]

<...>

> i have read both .. anyways this thread is about memory management. and we are discussing something else

Drifting a bit off-topic is not that bad - since we're still in "the area"

In my opinion it doesn't make sense trying to explain the "use" or "concept" of memory management without the background, what the operating system is really doing - not, that I would understand every detail of it but reading that book gives at least an overall understanding, how operating systems work internally.

Markus

[former_member759680]

i think there are two tanenbaums one who wrote the OS book and the other who wrote book on Computer networks.

I tihnk its the same guy - Andrew Tanenbaum

Refernce - http://en.wikipedia.org/wiki/Andrew_S._Tanenbaum

http://www.prenhall.com/tanenbaum/

P.S. Good read - http://en.wikipedia.org/wiki/Tanenbaum%E2%80%93Torvalds_debate

Edited by: Gautam Poddar on Oct 28, 2009 6:17 AM

[Former Member]

Actually, the main reason for this forum trail is to seek insights and perspectives from SAP Practitioners with their experiences and encounters. I would appreciate it if you could provide it yourself and not direct to sites and other sources. If I needed information from sites and other sources, I can simply research them myself.

[former_member185954]

Hello Jett,

I think you have mistaken the point here.

On every forum you have a thread called [Rules of Engagement|;.

In this thread, there is a link to a SDN Wiki Page which lays down the rules one needs to follow while posting to any of these forums.

However, since you do not 'LIKE' checking links, i am posting the rules here:

Asking & Answering in the Forums

Welcome! Before you post, please familiarize yourself with the rules of engagement.

Step 1: Finding An Answer

Rule number one: Try to find the answer first. There are tons of resources out there, show that you have tried to find the answer. A question that shows that the person is willing to try and help themselves is more likely to be answered than one which simply demands information. Tell us what you have done to try and solve the problem yourself - often we can learn from that too!

Obviously you should check SAP's online help, and if you have not looked for SAP Notes you should make the readers aware of this. Many SDNers are very helpful and will even search for SAP Notes for you if you don't have that possibility yourself, but many will assume that you have already searched for SAP Notes.

Search the forums, the articles, the blog posts and the Frequently Asked Questions (FAQ) in the Wiki for your topic.

Step 2: Asking Your Question

Once you have verified that no resources are available for solving your problem, ask your question. Do the following:

- Use a Good Subject Line

The subject header is your golden opportunity to attract qualified experts' attention in around 50 characters or less. Don't waste it on babble like "Workflow question". We all have busy jobs, often we just skim through the list headings and read those that interest us. Also, DO NOT reply to an unrelated post to ask a different question. This confuses those reading the thread and may lose people that would be interested in your question. Always start a new topic with a new mail.

Bad subject: Urgent problem with workflow

Good subject: Error after transport: "Inconsistent workflow definition"

Do not use words in capital letters and any of the words: urgent, quickly, burning, etc in your message. Especially not in the title! This just irritates and does not help you get to your goal. From our side, we definitely do not answer faster when we see these words.

The same goes for such things as ??? or !!! in appends. In the English language one ? or ! is sufficient to terminate a sentence.

- Only One Question Per Posting

For each question that you have, make a separate posting. Don't ask multiple questions in one posting, this is confusing for people and might not get answered, since the subject line does not reflect all your problems. If a new and unrelated question comes up during a thread, start a new thread.

- Provide Enough Information.

For starters, please tell us which version and type of system you're working on - e.g. SAP R/3 4.6C or SRM 4.0 (EBP 5.0). If your question is regarding an error, include that in the message. If it is a request for info, please be specific. Questions such as "How do I administer workflow" are vague, tell us exactly what you want to know - "I'm the administrator, how do I forward work items to another agent?". If it's a big query, its better to break it down into separate questions.

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The question you ask and the solution to it is often also interesting for other users of the community. If you ask somebody to send you the answer per email, you deprive others of also learning to know the answer. Therefore any requests for sending material or answers to an email address will be modified by the forum moderators.

- Re-read Your Query Before Submitting it.

Put yourself in a reader's position - does the question make sense? Can I understand the problem? Is this enough information to be able to answer the problem?

This is a very valuable technique, because many questions end up answering themselves when you read them carefully. It also leads to better questions. Many readers like good questions, especially if they are thought-provoking and thus help all of us understand things better. This is one of the main reasons many experienced consultants read the list regularly.

- Why is Nobody Answering my Question?

There may be a variety of reasons:

1) Never assume that you are entitled to an answer. Remember: this is a community forum; people have jobs just like you and respond voluntarily. Perhaps nobody knows the answer.

2) Did you give the other users enough time? Don't be impatient. If the question is urgent, go to the official service channels.

3) Is your subject misleading? your post in the right forum? your problem description understandable?

Step 3: Provide Feedback and an Update

Finally, it's nice to follow up with a brief update if you found the solution. People may try to help not because they know the answer, but because they are interested in solving the same problem; or people may just encounter the same issue in the future and be searching the archives. It's a good way to give back to the community, irrespective of whether you are a beginner or an expert.

Step 4: Thank Others by Giving Points

SDN/BPX has a Contributor Recognition Program. Which in short text means that for each question you have 10 points, which can be given to the person that answers your question. 6 & 2 points should also be given for helpful answers. For every question you later award points for, you in turn receive 1 point for.

Step 5: Answering a question

The community lives by people like you, trying to help others. When you see an unanswered question where you think you can answer, do so and help the poster. Remember to be polite and if you do not completely understand a question and need more details, request more information from the poster.

- Provide materials as attachment to a post.

As helpful material is, do not forget that other users might also be interested in your documents. Do not send them as email to the asking poster, but attach them to your answering post or in the appropriate wiki section. Its also possible to provide a publicly available link. Use the How to Contribute -> Content Submission System link on the SDN, the SDN platform team will upload the document for you and provide you with a link. This way you not only serve others but also yourself, by avoiding dozens of posts also asking for your material.

- Do not provide copyrighted material.

Do not offer copyrighted material, where you do not own the copyright. Soft copies of books, certification material, etc. often is copyrighted and even if you got it through other sources, do not send it around. The authors of this material have a right to have their material protected.

Why worry? At the end of the day, all of us are human, and a small recognition goes a long way. This way, you win in getting a good answer. The person answering gets that warm feeling of having helped and with enough points gets a small reward.

SDN/BPX is a community that lives for and from its users. Which means when asking a question, you also assume the responsibility to assign the points. Its recommended that you assign 6 or 10 points once to the answer/person that helped you the most. Assign 2 points to everyone that contributed something. See also FAQ.

SDN is a place where developers meet other developers and BPX where Business Process Experts meet others. One takes the time to see the problems other developers, consultants, experienced end users and business process experts are facing, the time to read possible solutions (to learn), and maybe one day the time to answer some questions.

Use Proper Language

The language that you use in the forum should not hurt the co-SDNer or BPXer. Please don't use curse, slang, inappropriate or otherwise offensive language. Every professional has the responsibility to maintain good relationship/environment around. This is a community but a professional one please keep that in mind as you converse with others here. Any abuses should be reported to the moderators if no acceptable resolution can be found.

Hope that helps.

Regards,

Siddhesh

[Former Member]

Hi Michael,

The roll area is used for the initial memory assigned to a user context.

Shared memory is memory that can be addressed by different processes as opposed to private memory that can only be addressed by the process that creates it.

A more important shared memory area is extended memory. In 32 bit processing you need to keep shared memory areas at a minimum because otherwise you limit the amount of space in the address space that your program can use for its own data.

SAP memory is a memory area to which all main sessions within a SAPgui have access. You can use SAP memory either to pass data from one program to another within a session, or to pass data from one session to another.

Buffer is temporary memory,for example the Program Buffer (PXA) this buffer hold the recently used programs in memory for fast access and needs to be read by all work processes,if all completed & not used for more time will be erased.

Just about different types of memories. If possible i will get back to you in detail.

Reward if helpful.

Arun

[Former Member]

Thanks Arun.

Could you provide more details what a Heap Memory is? What an extended memory is? Does it basically come from the Windows Page File? Does it imply that as long as there is a sufficient Page File, no memory related problems will occur?

[Former Member]

Hi,

check folloiwng

http://help.sap.com/saphelp_nw04/helpdata/en/75/358abcbcb911d5993a00508b6b8b11/content.htm

http://help.sap.com/saphelp_nw04/helpdata/en/7a/caa6f6bfdb11d188b30000e83539c3/frameset.htm

regards,

kaushal

[former_member185954]

Hello Jett,

Once you are clear with all the SAP Memory management concepts.

You might want to read up special settings for Windows OS.

Please go through the following link:

http://help.sap.com/saphelp_47x200/helpdata/en/02/9627af538111d1891b0000e8322f96/frameset.htm

Regards,

Siddhesh

[antonio_voce]

Hi ,

you can find good information here :

http://help.sap.com/saphelp_bw30b/helpdata/en/7a/caa6f3bfdb11d188b30000e83539c3/frameset.htm

I hope this can help you.

Antonio.