topic add memory in Operating System - HP-UX

add memory

Alberto Hurtado — Wed, 13 Oct 2004 18:42:50 GMT

Hi
My question is if shmmax must be increased due to an increase of phys. memory of 3500 to 6500 Mb. If this is correct in what proportion i must increase.

Thanks for your help

shmmax actual = 1,073,741,824

Re: add memory

Sundar_7 — Wed, 13 Oct 2004 18:55:10 GMT

shmmax only limits the size of the INDIVIDUAL shared memory segments. That means any shared memory segment created in the system should be of size less than or equal to shmmax.

So, it is rather dependent on the application you have running on the system. Increasing the physical memory doesnt necessarily require increasing shmmax parameter.

Now that you have more memory available for use, you could consider increaring shmmax, if the shmget() calls by your application is failing due to the size limit.

Re: add memory

Sridhar Bhaskarla — Wed, 13 Oct 2004 19:17:07 GMT

Hi,

If the OS is of 32bit or if your application is 32bit, there is no point increasing shmmax as you can't have a segment more than the size of a 32bit quadrant which is 1 GB.

If your application is 64bit, then you can probably increase it if it is required.

It's really your requirement not because there is more memory.

-Sri

Re: add memory

Steven E. Protter — Wed, 13 Oct 2004 19:33:24 GMT

I was taught that settings of shmmax greater than 25% of memory will be ignored.

Memory is defined as physical memory plus swap.

Oracle, apache and other apps are very hungry for shared memory and I generally max it out.

Within the limitations Sri presented you can increase shared memory two ways, by adding physical memory or by increasing swap.

You're doing the right thing, getting more bang for your buck.

SEP