Enable Cluster Time Synchronization Service on Oracle 11gr2 RAC

1) If Synchronization Service works with NTP   then CTSS must be in Observer mode. Lets check it:

[oracle@node1 ~]$grid_env
[oracle@node1 ~]$ crsctl check ctss
CRS-4700: The Cluster Time Synchronization Service is in Observer mode.

[oracle@node2 ~]$ grid_env
[oracle@node2 ~]$ crsctl check ctss
CRS-4700: The Cluster Time Synchronization Service is in Observer mode.

This means RAC works with NTP.

2) Now lets disable NTP

[oracle@node1 ~]$ su -
Password:
[root@node1 ~]# grid_env
[root@node1 ~]# crsctl stop crs
<<<output trimmed>>>
CRS-2793: Shutdown of Oracle High Availability Services-managed resources on 'node1' has completed
CRS-4133: Oracle High Availability Services has been stopped.
[root@node2 ~]# crsctl stop crs
<<<output trimmed>>>
CRS-2793: Shutdown of Oracle High Availability Services-managed resources on 'node2' has completed
CRS-4133: Oracle High Availability Services has been stopped.
[oracle@node1 ~]$ /sbin/service ntpd stop
[root@node1 ~]# chkconfig ntpd off
[oracle@node2 ~]$ /sbin/service ntpd stop
[root@node2 ~]# chkconfig ntpd off
[root@node1 ~]# mv /etc/ntp.conf /tmp/
[root@node2 ~]# mv /etc/ntp.conf /tmp/

3. Start the cluster on all nodes

[root@node1 ~]# crsctl start crs
CRS-4123: Oracle High Availability Services has been started.
[root@node2 ~]# crsctl start crs
CRS-4123: Oracle High Availability Services has been started.

4. Now let’s check ctss .  And we saw that ctss starts in active mode :

[oracle@node1 ~]$ crsctl check ctss
CRS-4701: The Cluster Time Synchronization Service is in Active mode.
CRS-4702: Offset (in msec): 0
[root@node2 ~]# crsctl check ctss
CRS-4701: The Cluster Time Synchronization Service is in Active mode.
CRS-4702: Offset (in msec): 0