SAP Memory Managemt parameters on AIX 6.1

[Former Member]

Hello,

please, can you explain me the significance of parameters ES/SHM_MAX_PRIVS_SEGS and ES/SHM_PROC_SEG_COUNT? I know that both parameters are described in SAP note #789477 and others, but I can not find the meaing of the two parameters.

Why is it important to setup the number of shared private segments?

Best regards

Martin Hucl.

[mercedes_fernandez]

Hello Martin,

the meaning of the parameters is:

ES/SHM_PROC_SEG_COUNT : Specifies the number of shared memory segments that are used as shared and privately.

ES/SHM_MAX_PRIV_SEGS: Specifies the number of shared memory segments that are used privately.

As mentioned in note 789477, the ztta/roll_extension = ES/SHM_MAX_PRIV_SEGS * ES/SHM_SEG_SIZE * 1024 * 1024

hope it helps,

Mercedes

[Former Member]

Hello Mercedes,

thank you for answer. I am sorry, I know the answers from SAP notes. But question is: Why I must specify the number of shared private segments? The answer may by: because the end user context is stored in extended memory. The EM is divided into parts according parameter ES/SHM_SEG_SIZE. And the private segments are necessary for internal purposes. Ok. Or the private segments are out of shared memory and are based on 256MB segments.

I am tunning memory management on AIX and I need to understood how it works. For example: Why I must specify the via parameter ES/SHM_SEG_SIZE the segment size? I see in SAP note #789477 "Addition Information" ... For each user context that allocate extended memory, at least one virtual, separate shared memory segment of 256 MB is created and also visible in "ipcs"...

I see via command "ipcs" lot of shared memories which are similiar to value of "ES/SHM_SEGS_SIZE". But I do not see any blocks with 256MB length.

Thank you very much for response.

Martin Hucl.

[mercedes_fernandez]

Hello Martin,

the user context is stored in Extended Memory, if If the user context still requires additional memory (apart from roll & Extended memory), it is assigned heap memory

With the Alternative Memory Management in AIX, multiple "windows" of extended memory are created where virtual shm segments for each user context. The size of these segments is determined by ES/SHM_SEG_SIZE and each user context can access up to ES/SHM_PROC_SEG_COUNT.

hope it helps,

Mercedes