Memory Tuning

[former_member185257]

Hi,

Our systems are on Windows Server 2008 and have MSSQL Server 2008 R2. But ST02, I found a lots of buffers are red. So want to tune SAP memory.

I have gone through the SAPNOTE 88416(Zero Administration) and checked that.

So, when a fresh system is installed on windows server, does it follows the zero administration parameters by default or we need to change to zero administration parameter?

Any help on this.

Regards,

Sk Nurujjaman

[Matt_Fraser]

Zero-Admin Memory Management is active by default for a fresh Windows-based installation. However, ZAMM does not tune the buffers -- you still must do those manually, based upon your own needs.

I believe for some of those buffers, a hit ratio in the 90-95% ratio would still be quite low, unless the machine has recently been restarted. It depends upon the buffer. If you are getting "red" statuses, that is probably based upon swaps occurring. In general, some amount of swapping is perfectly acceptable and to be expected, yet ST02 will turn the buffer to red if even a single swap has occurred. If you are getting an average of over 1000 swaps per day for some buffers, and hit ratios are not in the 98-99% range after about a week or more of operation, then you might consider increasing the size of the buffer. Double-clicking the buffer in ST02 will give you the opportunity to see which parameters are involved and to find some documentation about them.

Before increasing a buffer size, however, you want to ensure you have plenty of free extended memory. You can see this in ST02 as well. If Max Use is significantly lower than In Mem, then you probably have enough free memory to do this.

Also, are you actually observing poor performance on the server? Just because you are getting swaps does not by itself mean the server is not performing well.

Cheers,

Matt

[Former Member]

hi Matt,

>>Before increasing a buffer size, however, you want to ensure you have plenty of free extended memory.

Most of the buffers listed in ST02 are not stored in the extended memory. So it is not important how many free extended memory we have. Most of the buffers are own shared memory segments.

One thing is also worth to mention:

For some buffers (primary programs buffer) it is not necessarily a problem if you see swaps (and only the buffers with swaps are highlighted in ST02) here.

When double clicking on a buffer name in ST02 the second page shows more detailed information. Listen here to Hitratio or  DB access quality. For the program buffer you can easily have the situation that you have plenty of swaps and at the same time a DB access quality greater than 99 percent. For those who are interested in more details: Click on Buffered Object --> PXA Buffer technical and sort the list for column Used.

You will see that plenty of objects in the abap program buffer are only used once (a lot of them may be dynamically created code and will only be used once). If objects used only once before they are swapped out of the cache - this is normal for a cache and not necessarily a sign for a too small cache size.

Therefore:

1. look at the hitratio/db access quality before increasing buffers
2. when increasing buffers, increase them in small steps and always check for sufficient free memory in ST06 (sum of Memory Free and Swapfile Free)

regards

Peter

PS: you may also have a look to the command line utility sappfpar.exe for information on Shared Memory segments and SAP ABAP Server Instance Memory consumption:

sapntchk.exe check pf=<full path to an ABAP-Instance-Profile>

Shared memory disposition overview

================================================================

Key:        1  Size:         512 (   0.0 MB) System administration

Key:        2  Size:    62575168 (  59.7 MB) Disp. administration tables

Key:        3  Size:   208896000 ( 199.2 MB) Disp. communication areas

Key:        4  Size:     1073360 (   1.0 MB) statistic area

Key:        5  Size:        4096 (   0.0 MB) SCSA area

Key:        6  Size:  1251915776 (1193.9 MB) ABAP program buffer

Key:        7  Size:       33376 (   0.0 MB) Update task administration

Key:        8  Size:   140247540 ( 133.7 MB) Paging buffer

Key:       11  Size:      500000 (   0.5 MB) Factory calender buffer

Key:       12  Size:     6000000 (   5.7 MB) TemSe Char-Code convert Buf.

Key:       13  Size:    60500000 (  57.7 MB) Alert Area

Key:       14  Size:     4400000 (   4.2 MB) Presentation buffer

Key:       16  Size:       21360 (   0.0 MB) Semaphore activity monitoring

Key:       18  Size:      577880 (   0.5 MB) Paging administration

Key:       20  Size:    21555128 (  20.6 MB) New Table buffer tbi

Key:       21  Size:    11404032 (  10.9 MB) Request Queue Admin

Key:       30  Size:       44620 (   0.0 MB) Taskhandler runtime admin.

Key:       41  Size:    25010000 (  23.9 MB) DB statistics buffer

Key:       42  Size:    39451520 (  37.6 MB) DB TTAB buffer

Key:       43  Size:   129608816 ( 123.6 MB) DB FTAB buffer

Key:       44  Size:    27801616 (  26.5 MB) DB IREC buffer

Key:       45  Size:    15779856 (  15.0 MB) DB short nametab buffer

Key:       46  Size:         160 (   0.0 MB) DB sync table

Key:       47  Size:     3175424 (   3.0 MB) DB CUA buffer

Key:       48  Size:      552160 (   0.5 MB) Number range buffer

Key:       49  Size:     2224500 (   2.1 MB) Spool admin (SpoolWP+DiaWP)

Key:       51  Size:    35000000 (  33.4 MB) Extended memory admin.

Key:       52  Size:      180000 (   0.2 MB) Message Server buffer

Key:       54  Size:    85875712 (  81.9 MB) Export/Import buffer

Key:       56  Size:      535936 (   0.5 MB) Application statistics

Key:       57  Size:     1992294 (   1.9 MB) Profilparameter in shared mem

Key:       58  Size:        2076 (   0.0 MB) Enqueue ID for reset

Key:       62  Size:   180355072 ( 172.0 MB) Memory pipes

Key:       63  Size:      409600 (   0.4 MB) ICMAN shared memory

Key:       64  Size:     4227072 (   4.0 MB) Online Text Repository Buf.

Key:       65  Size:     4227072 (   4.0 MB) Export/Import Shared Memory

Key:       73  Size:    60211232 (  57.4 MB) CCMS Extended Alert Area

Key:       76  Size:     1185920 (   1.1 MB) Ext. Segment Administration

Key:       77  Size:       35008 (   0.0 MB) Ext. Memory Administration

Key:       78  Size:        4272 (   0.0 MB) Ext. Global Memory Admin

Key:       81  Size:       35184 (   0.0 MB) Security Audit Log

Key:       83  Size:    74448896 (  71.0 MB) ABAP Coverage Analyzer

Key:       85  Size:       53264 (   0.0 MB) ACM Trace and others

Nr of operating system shared memory segments: 44

Shared memory resource requirements estimated

================================================================

Total Nr of shared segments required.....:         44

Shared memory segment size required min..: 1251915776 (1193.9 MB)

Swap space requirements estimated

================================================

Shared memory....................: 2348.5 MB

Processes........................:  153.7 MB

Extended Memory .................: 5732.0 MB

------------------------------------------------

Total, minimum requirement.......: 8234.2 MB

Process local heaps, worst case..: 8189.0 MB

Total, worst case requirement....: 16423.2 MB

[Matt_Fraser]

Learn something new every day! I thought there was a relationship between the extended memory shown in ST02 and the memory shown in ST06. Since the extended memory "In Mem" number shown in ST02 pretty much equals the physical RAM (or PHYS_MEMSIZE) of the server, it's difficult to imagine how the buffers have any room outside of this for a dialog instance where PHYS_MEMSIZE is not set.

So, Peter, are you advising that we should set PHYS_MEMSIZE in this case to a lower value to provide room for the buffers outside of it? Most of them are not significantly large, of course, but the program buffer can be quite large in some circumstances (about a gigabyte in your example, and that is what I currently have set on my app servers, too).

[former_member185257]

Thanks all for your valuable information.

Could you please guide me a reference link or document for 721 kernel.

Thanks,

Nurujjaman

[Sriram2009]

Hi

Refer the SAP Note   1713986 - Installation of kernel 721 (EXT)

1975687 - SAP Kernel 7.21 (EXT) replaces SAP Kernel 7.20 (EXT) as standard kernel in Q1/2015

Regards

SS

[former_member185257]

What rubish Sriram. I dont ask any link for Kernel 721 installation.

Please read the previous comments first , then try to suggest.

[Sriram2009]

"Could you please guide me a reference link or document for 721 kernel."

What reference link or document your waht tell ? Are your looking like refer of SAP note?

1728283 - SAP Kernel 721: General Information

[former_member185257]

This discussion is for Memory tuning and I am asking the reference doc of Memory tuning of ABAP system with Kernel 721.

[isaias_freitas]

Hello,

I'm not sure whether ZAMM (Zero Administration Memory Management) will be used by default at a fresh installation.

In either case, ZAMM will basically define default values for each memory area. That's it.

It will not remove the need to tune some memory parameters based on your own system needs / behavior.

About the ST02 buffers in red, how is the hit ratio?

As far as I know, if the hit ration is high (say, 90% - 95% or more), you would not need to worry about red buffers.

However, if the hit ratio is low, you should consider increasing the size of the related buffer.

Regards,

Isaías