os: [root@oracle ~]# cat /etc/redhat-release CentOS Linux release 7.2.1511 (Core)
Fri Nov 23 10:25:34 2018 Errors in file /home/app/oracle/diag/rdbms/oracrm/oracrm/trace/oracrm_dbw2_20900.trc: ORA-27157: OS post/wait facility removed ORA-27300: OS system dependent operation:semop failed with status: 43 ORA-27301: OS failure message: Identifier removed ORA-27302: failure occurred at: sskgpwwait1 Errors in file /home/app/oracle/diag/rdbms/oracrm/oracrm/trace/oracrm_dbw3_20902.trc: ORA-27157: OS post/wait facility removed ORA-27300: OS system dependent operation:semop failed with status: 43 ORA-27301: OS failure message: Identifier removed ORA-27302: failure occurred at: sskgpwwait1
The semaphores used by Oracle have been inadvertendly removed The errors are signalling that something happened at the OS level with shared memory and/or semaphores. The semaphore sets could be removed manually, or they could be dying for some reason due to a hardware error. Either when remounting the /dev/shm or You may want to check for any possibility of a user dba using the "ipcrm" command to kill the semaphores (accidentally) since the error ora-27301 (OS failure message: Identifier removed) suggests that. Also, it could have been a bad memory stick or something else at the OS level. Someone could also have removed the shared memory segments at the OS level for some specific reason, or by accident. Most likely something had removed the shared memory and semaphore sets in use by 'oracle'. This can only be done by a root-level user or 'oracle' itself who owns the resources. If someone logged in as root and removed all IPC resources, Oracle would crash when it lost the allocated shared memory/semaphores.
This could be due to some outside user or application removing the semaphores/shared memory.
To monitor the semaphore/shared memory state we can use the following methods:
Setup a cronjob to run every 5-10min and dump the output of 'ipcs' and 'ps - ef' to a file with a timestamp.
Rotate your logs every 4-7 days to build a history.
Then if the problem re-occurs, we can at least try to make sure 'ipcrm' wasn't the culprit and get some general information of the state of the IPC resources plus the processes running.
You can also consult with your sysadmin to check if there is any OS level auditing that can be turned on to audit the usage of commands like 'ipcrm' which can remove shared memory segments /semaphore sets.
Note: This issue can happen on different platform, but in case you encounter the issue in RHEL7.2, then please also check below RHEL7.2 specific information.
In RHEL7.2 operating system setting RemoveIPC=YES crashes the database.The default value for RemoveIPC in RHEL7.2 is YES.
1) Set RemoveIPC=no in /etc/systemd/logind.conf if it is not in that file
2) Reboot the server or restart systemd-logind as follows:
# systemctl daemon-reload
# systemctl restart systemd-logind
Migrate to Oracle Linux 7.2 resolves the problem.
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