You have the relationship inverted in your statement.
"The problem is that SEMMNS has to be larger or equal than SEMMSL*SEMMNI"
From Redhat
THE SEMMNS PARAMETER
This parameter defines the total number of semaphores (not semaphore sets)
for the entire Linux system. A semaphore set can have more than one
semaphore, and as the semget(2) man page explains, values greater than
SEMMSL * SEMMNI makes it irrelevant. The maximum number of semaphores that
can be allocated on a Linux system will be the lesser of: SEMMNS or (SEMMSL
* SEMMNI).
Again without the trace file we do not know what Oracle support was looking
to change with those settings. If it is a semaphore problem and not a
semaphore set or semaphore operation problem, then I would say that SEMMNS
would also need to be increased to go along with the SEMMSL and SEMMNI
increased settings. However, if the problem they are trying to fix is a
semaphore set or semaphore operation problem then changing SEMMNS too, may
not be necessary. Only the trace file or gdb of the core file will tell.
From: oracle-l-bounce@xxxxxxxxxxxxx <oracle-l-bounce@xxxxxxxxxxxxx> On
Behalf Of Mladen Gogala
Sent: Saturday, February 13, 2021 9:57 AM
To: dimensional.dba@xxxxxxxxxxx; oracle-l@xxxxxxxxxxxxx
Subject: Re: linux kernel parameters
The problem is that SEMMNS has to be larger or equal than SEMMSL*SEMMNI.
Ideally, SEMMNS=SEMMSL*SEMMNI and SEMMSL=SEMOPM.
Semaphores are a subsystem governed by a device driver and have certain
syntax. No recommendation which doesn't follow that syntax can be valid.
Regards
On 2/13/21 1:22 AM, dimensional.dba@xxxxxxxxxxx
<mailto:dimensional.dba@xxxxxxxxxxx> wrote:
There are varying Documents in Oracle Support of Oracle troubleshooting
problems and some of the values in the notes actually state the value for
those 2 parameters can be up to 32000 on RHEL6 (Doc ID 2467427.1).
On most of the Exadatas I manage with out of the box settings (UEL6/7) those
values are set to 2048.
--
Mladen Gogala
Database Consultant
https://dbwhisperer.wordpress.com
