Startup fails with ORA-27154: post/wait create failed

The other day I was getting a strange message trying to bring up one of our Oracle 11g databases; on the same box, we have about 25 instances:


SQL> startup
ORA-27154: post/wait create failed
ORA-27300: OS system dependent operation:semget failed with status: 28
ORA-27301: OS failure message: No space left on device
ORA-27302: failure occurred at: sskgpcreates

The error messages in this case are misleading, in my case there was no disk space issue. Many articles point in the direction of a issue with the number of UNIX semaphores in the system.

In my case, by decreasing the PROCESSES initialization parameter to 200, down from 800, solved the issue and the database came up.