topic Re: semaphores question in Operating System - HP-UX

semaphores question

Filosofo — Fri, 07 Apr 2006 05:52:48 GMT

Hi all,
I have a question about semaphores....My kernel parameters for semaphores are:

semmni 20992
semmns 31488
semmnu 10492
semmsl 2048
semume 10496

I suppose to exceed a max value, for example, of kernel parameter semume, I can see an error meesages in to syslog.log ?

Regards

Re: semaphores question

Steven E. Protter — Fri, 07 Apr 2006 06:01:15 GMT

Shalom Filo,

Probably no message to the logfile.

You may see a warning when you compile the kernel. It is possible however to create an unbootable kernel.

For most parameters, when you exceed the max value, the OS simply ignores you and uses teh max value.

An example is ORACLE AS 10g, which requires SHMMAX to be equal to physical memory. 11i v1 and below ignores settings more than 25% of memory, which is defined as ram plus swap.

You set the value higher anyway, oracle is happy and the system ignores the setting.

SEP

Re: semaphores question

RAC_1 — Fri, 07 Apr 2006 06:30:05 GMT

You can monitor real time usage with ipcs -s

If your OS is 11i, V2, you can define kernel alarm that will get triggered when defined threshold is crossed.
man kcalarm
man kcuasage.

Re: semaphores question

A. Clay Stephenson — Fri, 07 Apr 2006 09:29:21 GMT

What you will see are application errors (specifically system calls failing and setting errno to some value). To the extent that the application logs these errors (either to a simple file or to syslogd), you will have the diagnostics that you need.
This is why good system admins make themselves intimately familiar with the man 2 pages (the system calls) --- even if they are not programmers.