apr_proc_mutex_lock failed. Attempting to shutdown process gracefully

Error:
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[OHS] [INCIDENT_ERROR:10] [OHS-9999] [core.c] VirtualHost: main] (37)No locks available:  apr_proc_mutex_lock failed. Attempting to shutdown process gracefully.

This is what yo will see in the OHS log and http://ohshost:ohsport/ will give a 404.

This happens mostly when you install OHS instance on a shared drive (i.e., NFS). the lock file is the culprit.

OHS version: 11.1.1.7
OS: RHEL 6.6

Solution:
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Take a backup of httpd.conf
Locate module mpm_prefork_module and mpm_worker_module in httpd.conf. Observe that the LockFile is pointing to the path on shared drive.
This needs to be changed to a folder local to the server where you have your OHS instance running.

Modify it as below

<IfModule mpm_prefork_module>
StartServers         5
MinSpareServers      5
MaxSpareServers     10
MaxClients         150
MaxRequestsPerChild  0
AcceptMutex fcntl
LockFile " <LOCAL_DISK_PATH>"
</IfModule>

<IfModule mpm_worker_module>
StartServers         2
MaxClients         150
MinSpareThreads     25
MaxSpareThreads     75
ThreadsPerChild     25
MaxRequestsPerChild  0
AcceptMutex fcntl
LockFile " <LOCAL DISK_PATH>"

Save the httpd.conf file and start OHS.