shmmax value

[Amit Manna_5]

I have a HP system OS version is 11.0 for
shmmax value is as follows:
kmtune -l -q shmmax
Parameter: shmmax
Value: 0XC0000000
Default: 0X4000000
Minimum: -
Module: -


Total VM : 1012mb Sys Mem : 244.7mb User Mem: 2.78gb Phys Mem: 4.00gb
Active VM: 257.9mb Buf Cache: 614.4mb Free Mem: 386.2mb

We are planning to upgrade the physical memory from 4 GB to 6 GB.

Do we need to increase the shmmax value and if yes to what value

What would be procedure for increasing it


many thanks in advance

[Johnson Punniyalingam]

Hi Amit,

>>We are planning to upgrade the physical memory from 4 GB to 6 GB.<<

Your swap space should be double the size of your Pshyical RAM

if total Pshyical RAM 6GB you need have totol swap space of 12GB

# swapinfo -tam (Can check current size of you swap)

>>Do we need to increase the shmmax value and if yes to what value<<<

NO NEED

what Application are you running.?
do you have any perfromance issue?

Please below Thread for more Inforamtion

http://forums11.itrc.hp.com/service/forums/questionanswer.do?threadId=1272448

Thanks,
Johnson

[Mel Burslan · Accepted solution]

>We are planning to upgrade the physical
>memory from 4 GB to 6 GB.
>
>Do we need to increase the shmmax value and
>if yes to what value

The answe is it depends, but more than likely it will be to your benefit to increase this value.

Most java-heavy applications running on hpux (and what is not java-heavy nowadays) wants you to set shmmax value to value which is equal to the amount of physical memory. Right now, you are saying you have 4GB physical memory on the system but your shmmax is set to 3GB. If it is configured like this for a reason, you need to figure out why it is that way and adjust the value according to the requirements of the person/vendor who wanted it that way. This will help you avoid headaches down the road.

If you are running Oracle, SAP, or any other java written application, in the lack of finding out what shmmax value needs to be, it is a safe bet to set it to the amount of physical memory, which will be 6GB in your case. SO the command to modify it should be as follows:

kmtune -s shmmax=6442450944

ans it is a dynamically configurable parameter, not needing a reboot.

Hope this helps

[Tingli]

I think in oracle, the shmmax should be larger than the largest sga.

[Emil Velez]

shmmax is the size of the largest shared memory segement that a program can create. A program can attach to multiple shared memory segments but this parameter is the largest size of a single shared memory segment.

Defer to your applications kernel parameter requirements.

[Amit Manna_5]

Does this parameter increase dont need reboot/

[Ganesan R]

Hi Amit,

Changes to this tunable take effect immediately and does not need reboot.

Check this..

http://docs.hp.com/en/B2355-60127/shmmax.5.html

[Steven E. Protter]

Shalom,

Do you need to increase shmmax? No.

It might improve performance of applications like Oracle.

In this case I would do as follows:
sam
Kernel
Configurable parameters
Change shmmax

Compile kernel and boot via the menu.

Note: HP-UX 11.00 is out of support. I strongly urge a make_tape_recovery or make_net_recovery backup be done before any changes.

SEP

[Sharma Sanjeev]

Hi Amit

Its not required to increase the value of shmmax after upgrade of memory but you can always increase it.

Its a Static value and requires reboot in 11.00

Regards
Sanjeev

[Sharma Sanjeev]

Hi Amit

As you mentioned hp-ux version is 11.00 and in this version shmmax is static

shmmax 3221225472 3221225472 Static N/A

but not in 11.23

so it will require reboot after changing the value

Regards
Sanjeev