Oracle Distilled

When installing Oracle 11gR2 Grid Infrastructure either the cluster verify utility or the prerequisite checks find that the NTP daemon does not have the slewing option set.

- PRVF-5439 : NTP daemon does not slewing option "-x" set
  on node "ordrac1"
  - Cause: NTP daemon on the specified node does not have the
  slewing option set
  - Action: Shutdown and restart the NTP daemon with the
  slewing option set. For more information on the NTP daemon
  slewing option refer the NTP daemon's man pages.

What is slewing?

The NTP daemon will periodically update the system clock with the time from a reference clock. If the time on the reference clock is behind the time on the system clock, the system clock will be set backwards in one large decrement. Such swift changes in time can lead to Oracle shutting down the node due to inconsistent timers. To avoid this problem, NTP can be configured to slew the clock. When slewing the clock the time on system is incremented slower until the system clock is in sync with the time on the reference system.

How to set up slewing

Stop the NTP service on the node.

[root@odrac1 ~]# service ntpd stop
Shutting down ntpd:                                        [  OK  ]
[root@odrac1 ~]#
[/text/]
Edit the file <code>/etc/sysconfig/ntpd</code>
1
# Drop root to id 'ntp:ntp' by default.
OPTIONS="-u ntp:ntp -p /var/run/ntpd.pid"

# Set to 'yes' to sync hw clock after successful ntpdate
SYNC_HWCLOCK=no

# Additional options for ntpdate
NTPDATE_OPTIONS=""

Change the line

OPTIONS="-u ntp:ntp -p /var/run/ntpd.pid"

to

OPTIONS="-x -u ntp:ntp -p /var/run/ntpd.pid"

After saving the file restart the NTP service. Re-execute the cluster verify utility or the prerequisite checks.