Kernel parameter - semmns

[Sam Dee]

Hi Gurus,

Please I would like to know the max. value for the kernel parameter semmns (semaphors) . My Oracle guys want us to increase this value but we don't know the max it can take.

Hoping to hear from you soon

Sam

[Navin Bhat_2 · Accepted solution]

This is memory limited. default is 128 and minimum is 2.

[Sanjay_6]

Hi Sam,

This may help,

http://docs.hp.com/hpux/onlinedocs/939/KCParms/KCparam.SemMNS.html

Hope this helps.

Regds

[Geoff Wild]

Don't know max, but this is what we set it to:

SEMMNS 500
Maximum number of individual IPC semaphores available to system users, system-wide

Attached is a Oracle 8i Requirements on HP-UX


Rgds...Geoff

[Fred Ruffet]

I can't see any doc more explicit than "memory limited". I have here a machine where it is set to 8192... I think this is already high. What do they want you to set ?

Regards,

Fred

[Dani Seely]

Hey Sam,
What version of HP-UX are you referring to so you can be sure the max value is appropriate for your version?

SEMMNS is the setting for the total number of Semaphores allowed system wide and may differe between versions.

Oracle Support typically does not recommend specific values for semaphore kernel
parameters. Instead, use the information provided in this document to set the
parameters to values that are appropriate for your operating environment.

For more info on setting Oracle SEMAPHOREs, look at the following link:
http://www.dbforums.com/t497029.html for calculating Oracle's SEMAPHORE requirements.

[Dani Seely]

Hey Sam,
Meant to also ask, what version of Oracle are you referring to?

Based on configuring SEMAPHOREs for Oracle ... For every "processes=" in the init"SID".ora Oracle needs one semaphore (semmns).

Also, there's a good bit of information about kernel paramater configuration for Oracle at: http://www.orafaq.org/faqdbain.htm

This is a good read and reference site. Hope this helps.

[Sam Dee]

Hi All,
Sorry, I could not reply early enough because of some internet problems with my PC.
I am running HP-UX 11i with 2GB RAM. The Oracle version is 8i. They want me to set the semmns value to 760 because they want to run 2 instances on the same box.

Regards

Sam

[Bruno Ganino]

Hi Sam, max value for semmns is 32000.
Bruno

[Bruno Ganino]

Generally
SEMMNS = Sum of all PROCESS parameter of all Databases on the machine +
the largest one again + 10 for each database

This is intersting
http://www.smart-soft.co.uk/Oracle/oracle-collaboration-suite-installation-guide.htm

HTH
Bruno

[Victor BERRIDGE]

Hi,
My advice would be:
semmni (NPROC)
semmns (SEMMNI*2)
semmnu (NPROC-4)

You increase maxusers? I has an impact on NPROC.. etc...

like that you dont have to fight with a value..
I have configured a few 11i boxes like that and it seems to do the job

All the best

Victor

[Dani Seely]

Hey Sam,
Thanks for the additional info. You should have no problem setting semmns to 760, however, your question was to "know the max" ... I believe Bruno is correct @ 32000. We are running Oracle 9i and our parameters are:

SEMMAP=128
SEMMNI=128
SEMMNS=32000
SEMMSL=250
SEMOPM=250
SHMMAX=1073741824
SHMMAXPGS=65536
SHMMNI=4096
SHMSEG=4096

Good luck!