Common Linux semaphore problems in Oracle

Oracle problems and errors involving Linux semaphores often indicate insufficient or improperly configured semaphore resources on that Linux system. Semaphore resources may need to be optimized before Oracle runs properly. Semaphore problems during startup Oracle allocates all the semaphores it needs for the background processes at database startup. The Oracle init.ora processes parameter determines the number of semaphores that will be allocated for Oracle use. If Oracle requires more semaphores than are allowed in one set, additional sets are allocated to Oracle. The following error codes are common startup errors. Error Cause ORA-7251 spcre: semget error, could not allocate any semaphores No semaphores are configured, or every semaphore is currently allocated. ORA-7252 spcre: semget error, could not allocate semaphores The first full set of semaphores was successfully allocated, but additional sets could not be allocated. ORA-7279 spcre: semget error, unable to get first semaphore set The system is attempting to allocate the first set of semaphores. The system either does not have sufficient semaphore resources or too many semaphores or semaphore sets are already allocated. The corrective actions for all three of the preceding errors are the same: Check semaphores in use. Verify all unused semaphores are reallocated. Rebuild Linux kernel to allocate additional semaphore resources. Semaphore during shutdown abort When a shutdown abort is performed, Oracle background processes are killed and semaphore sets are reallocated, without waiting for the user processes to finish. The following error codes are common shutdown abort errors: ORA-7264 spwat: semop error, unable to decrement semaphore ORA-7265 sppst: semop error, unable to increment semaphore Cause Action One or both of these error codes is displayed as a result of the following scenario: after a shutdown abort, one or more users ends a request to the database and the request process dies. This occurs because the attempt to increment or decrement the semaphore fails. This is an effective (though ungraceful) way of letting the users know that the database has been shut down with the abort option.