KB31895: How to set SEMMNI in Redhat Enterprise Linux

SYMPTOM:
 
When installing Strategy 9.x or 10.x on Redhat Linux following warning appears:
 

 
Sample Code/Error
Setup has detected that the following kernel parameters in your OS do not meet the requirements of Strategy 9 or 10. Maximum number of system wide semaphore sets (semmni). Required 2048, Current 128.
 
CAUSE:
 
This is because the SEMMNI setting does not meet Strategy Installation requirement.
 
Semaphores can be described as counters which are used to provide synchronization between processes or between threads within a process for shared resources like shared memories. System V semaphores support semaphore sets where each one is a counting semaphore. So when an application requests semaphores, the kernel releases them in sets. SEMMNI is one of semaphore settings in System V kernel. This parameter defines the maximum number of semaphore sets for the entire Linux system. This setting can greatly affect Strategy product performance for large scale production applications on Linux machines by configuring shared memory resources.
 
Strategy recommends SEMMNI value to be 2048. (Refer to product manual > Installation Configuration Guide > Chapter 1 Planning your Installation)
 
ACTION:
 
Change SEMMNI parameter as the following steps:
 
 

1. Add a line "kernel.sem=250 32000 32 2048" in /etc/sysctl.conf using VI or other plain text editor.    If kernel.sem line exsits, modify the existing values to 250 32000 32 2048.
    
   
2.  To make the setting effectted immediately, switch to root user and run "/sbin/sysctl -p" in terminal then check the SEMMNI value again by running "cat /proc/sys/kernel/sem" in terminal.
    
   

 
 
The SEMMNI value has been modified as in the picture.
 
NOTE:
TO LIST ALL SEMAPHORE SETTING:
 
Run "ipcs -ls" or run "cat /proc/sys/kernel/sem" in terminal.
 

 
The values from left to right are SEMMSL, SEMMNS, SEMOPM, and SEMMNI. By default SEMMNI value in Redhat Enterprise AS4 is 128.