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shmmax parameter

Nora Chiu
Occasional Visitor

shmmax parameter

I am running HPUX 11.0 with Sybase 12.0, I have 10GB physical memory.

1. I'd like to increase shmmax parameter, does anyone know the threshold value? I was told by one source that you can set it to 0xffffffff (max value) -OR- 50-60% of physical memory to be on the safe side. I was told by another source that HPUX may have a 2GB limitation.

BTW, I am not a DBA so any information would be helpful
James R. Ferguson
Acclaimed Contributor

Re: shmmax parameter

Hi Nora:

'shmmax' defines the system-wide maximum allowable shared memory segment size in bytes. Its minimum value is 2048 bytes. Its
maximum value is 0x40000000 (1024 MB) on 32-bit systems and 1TB on 64-bit systems. The default value is 0x04000000 (64 MB).

For more information on configurable kernel parametes, see:

Nora Chiu
Occasional Visitor

Re: shmmax parameter

David Snider
Frequent Advisor

Re: shmmax parameter

Thanks James,

According to the article you directed me to, it is possible for Oracle to use more than 1.75 GB of RAM.. But I need the Memory Windows product.. Is this something that must be purchased? Or can I download it..


Here is a snippet of my ipcs command
#ipcs -mopb
IPC status from /dev/kmem as of Fri May 11 09:29:13 2001
Shared Memory:
m 155 0x00000000 --rw-rw---- oracle dba 9 1073741824
m 156 0x5bc5a610 --rw-rw---- oracle dba 9 518119424

One segment is exactly 1GB, the other is about 518MB..

Also, according to HP, the maximum setting for SHMMAX in HP-UX 64-bit is 1 TB.. not 1792 MB..

Check out this link for more info..
David Snider
Frequent Advisor

Re: shmmax parameter


Posted my reply to the wrong message.. Please ignore it.. :-)
Pedro Sousa
Honored Contributor

Re: shmmax parameter

Sorry James, from the site information it is correct, but from sam's help, it isn't!
Specify system-wide maximum allowable shared memory segment size.
Acceptable Values:
Minimum: 2 Kbytes
Maximum: 1792 Mbytes
Default: 0x04000000 (64 Mbytes)
Joseph C. Denman
Honored Contributor

Re: shmmax parameter

I thought you answered it very well James.

1pts?????????? I would have given you the max, not that you needed them.

Nora sure a bit stingy with pts.

If I had only read the instructions first??