SAP System Hangs on my AIX 5.3 server

[Former Member]

Dear Experts,

We are on ECC 6.0, Oracle (10.2.0.2) and AIX 5.3 64 Bit OS, in the recent times we have been facing various issues concerned to our system performance which is a serious threat to our daily business.

We are having running this machine on 20 GB of physical memory and we are around 100 users.

The system every now and then hangs and when makes it impossible for the SAP users to login and work, when we run "TOPAS" command at the OS level it shows that the CPU utlization is very mimimal for any of the processes that are running. But very stange thing i noticed was that the RAM utlization was 99 % most of the times we encounter this problem.

The only remedy we saw during this problem was a "system bounce" which is not the correct solution.

I request your valuable inputs and suggestions on this, plz do reply

Thanks in advance

Regards

Hunky

[sivaramakrishn · Accepted solution]

Hi Hunky,

The notes are relevant as it for SAP versions 620 and above, The main change is that the memory management is changed from UNIX_STD to SHM_SEGS allowing AIX to manage memory according to its best pratices and hence get the best performance out of the box. I would strongly suggest you implement this note.

As for ML. it stands for Maintenance Level (akin to AIX patch level). So, your AIX 5.3 will be on ML 08 or 09 or something like that. SAP recommends a certain minimum ML level for each AIX version (you might find this information in PAM or in OSS Notes)

Also, check with your OS admins if they see any issues in the OS log (errpt -a). This will show if something else is eating away your memory or if there are hardware issues,

Regards

Siva

[Former Member]

I am having a similar problem that memory is being utilization is 99 % I have looked at all the notes mentioned and all the settings are all correct ,so how did you over come the problem?

Did you get a solution form SAP?

Regards

Simon G

[Former Member]

Dear Sive,

Thank you for all your inputs, i will surely follow all the suggestions given by and make sure that i will come out with all possible and correct information so that i can further narrow this issue.

All your suggestions are really helpful.

Thanks in advance

Regards

Hunky

[sivaramakrishn]

Hi Hunky,

PSALLOC is an environment variable (would be set under user <sid>adm) and is a mechanism used to allocate shared memory early for command execution. The default is late. This can be checked by using the env command (or ask your Unix admins if you are in doubt). The note says that this should not be set as there would be performance issues. Hence, if it is set, please remove.

As for the parameters you have mentioned, some are set. The others which are not set will have some default values (check this via RZ11). I also see that some parameters have non-standard values (heap_area* parameters & a value of zero is highly surprising!).

What I suggest is this --> Unless you have set these parameter values based on some earlier issues or SAP recommendations, change the paramater values to the values given in the OSS Note. If you want to reset a parameter back to the default value, simply delete the parameter set in the profile and it will go back to default.

You need not change the ES/SHM values as of now.

Also, check the system continously to find out what is causing the memory overload. Use ST06 to check memory consumption and to analyze past data. Also, check with your Unix team if they can pin point to which process is consuming a lot of memory.

Other than that, if there are other applications running on the same server, it might help to stop them and observe. Check this note -> 884393 - AIX saposcol consumes large amount of memory.

If this is happening on production systems, I would suggest opening a customer message with SAP as well to avoid delays.

Regards

Siva

[Former Member]

Dear Siva,

Thanks for your inputs, but if you consider the SAP Note: 789477 the following are the parameters that are already set on my system

PSALLOC=EARLY (No idea what this means) --> request your help on this

ES/TABLE = SHM_SEGS (parametera set on my system)

ES/SHM_SEG_SIZE= (parameter not set)

EM/TOTAL_SIZE_MB = (parameter not set)

em/global_area_MB = (parameter not set)

ztta/roll_extension = 2000000000

ztta/roll_area = 3500000

ztta/roll_first = 1

abap/heap_area_total = 5000000000

abap/heap_area_dia = 3000000000

abap/heap_area_nondia = 0

ES/SHM_PROC_SEG_COUNT= (parameter not set)

ES/SHM_MAX_PRIV_SEGS = (parameter not set)

ES/SHM_USER_COUNT = (parameter not set)

ES/SHM_SEG_COUNT = (parameter not set)

Now i request you to kindly help me based on my AIX server with 20GB physical memory and 38 GB of SWAP space.

Also Siva when i noticed my server it shows that the SWAP space that is configured is hardly being utilised.

I request you to kindly help me on this.

Thanks and million for all your comments and i have awarded suitable points already

Regards

Hunky

[Former Member]

Dear Siva,

Thank you very much for your quick and helpful reply.

But FYI we are on 700 Kernel release and in this case will the SAP Notes suggested (620) help me.

And also can you please help me understand SAP recommended ML for AIX 5.3 please.

Awaiting for your reply

Thanks in advance

Regards

Hunky

[sivaramakrishn]

Hi,

Check your virtual memory settings. Also, for AIX, it is advised that you use the special implementation of extended memory to optimize memory usage.

Please refer the following notes:

789477 - Large extended memory on AIX (64-bit) as of Kernel 6.20

191801 - AIX 64-bit with very large amount of Extended Memory

973227 - AIX Virtual Memory Management: Tuning Recommendations

I have used the settings in note 789477 to good effect in my previous projects and am sure that would help to solve your problems.

Also, make sure that you are on the SAP recommended ML versions of AIX for 5.3

Siva