Oracle Processes & SEMMNS

Parameter Background:
PROCESSES specifies the maximum number of operating system user processes that can simultaneously connect to Oracle. Its value should allow for all background processes such as locks, job queue processes, and parallel execution processes. An acceptable range of values is 6 to operating system-dependent.

The maximum value of the processes initialization parameter is dependent on the HP-UX 11.0
kernal parameter SEMMNS. Testing has indicated that Oracle reserves eighteen semaphores for some undocumented purpose.

If increasing the value of PROCESSES results in
ERROR on startup of the Oracle instance:

SQL> startup
ORA-24323: value not allowed
ORA-27146: post/wait initialization failed

Resolution:
Increase the value of SEMMNS to be at least 18 higher then the maximum value you require for PROCESSES.


Example:
If your kernal parameter is set to:
SEMMNS = 500

The maximum number of processes that Oracle will let you start the instance will be:
PROCESSES = 482