Blog Archive

Tuesday, 25 January 2005

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