How to increase shared memory

[uspfoms]

What Kernal settings control
the max size of shared memory
segments on HP-UX 11.0 ? Getting errors from Oracle:
ORA-00604:(Unable to allocate 4048 bytes of shared memory). Not sure if this is a UX or Oracle setting that determines the size of shared memory.

[James R. Ferguson]

Hi:

Kernel parameters starting with 'shm' are related to shared memory. For more information on 11.0, see here:

http://docs.hp.com/hpux/onlinedocs/939/KCParms/KCparams.OverviewAll.html

Regards!

...JRF...

[Stefan Farrelly]

Its an HP-UX kernel parameter. 2 to be exact, you should bump all both;

shmmax (this is the main one - usually set to some large number in the hundreds of MB or even GB!)
shmmni (usually set to 1000+)

[A. Clay Stephenson · Accepted solution]

The parameter is shmmax. However, and especially if you are running 32-bit 11.0 (or 32-bit Oracle) then you may be hitting other constraints like crossing a 1 GB memory boundary called a quadrant. In 64-bit 11.0, you can use memory windows and enable SHMEM_MAGIC using the chatr command to allow a process to span quadrants.

The other thing that can caise problems is fragmentation of memory. There may simply not be a large enough area to allow a shared memory segment of a given size.

If both the OS and application are 64-bit then essentially all constraints are removed and you are really only limited by shmmax and shmseg.


THe other possible tunanle paramter to check is shmseg - the maximum number of shm segments that can be attached by a single process.

[Sridhar Bhaskarla]

Hi,

Is this oracle a 32-bit one?. If so, you are limited to a max size of 1.75 GB for total shared memory. Or depending on the fragmentation done between the Shared Memory Quadrants, you may be getting this error too even if it is less than 1.75. Do an ipcs -mob and calculate the total of all the shared segment sizes owned by 32 bit processes.

If yours is a 64 bit version, then it could be oracle issue itself. I remember my DBA adjusting a parameter sometime back (shared_pool_size)??

-Sri

[steven Burgess_2]

Hi

http://www4.itrc.hp.com/service/cki/docDisplay.do?docLocale=en_US&docId=200000062945638

HTH

Steve

[uspfoms]

Thanks all, I'll try these suggestions.

[MANOJ SRIVASTAVA]

Also I am attaching a list of kernel paramter from one of our N class servers which runs 5 Oracel instances with 8.0gb RAM , so this can be some refernce place .



Manoj Srivastava