hwclock and date

We use RAC with Linux, Standard Edition RAC, 10g with 2 nodes with no more than 2 CPUs per machine. Today i’ve encountered a systemistic anomaly. Some time ago i’ve noticed that time in a RAC instation was different between the two nodes. SO is Linux Suse EL 9. System administrator did not configured a sincronization mechanism for time so during a downtime period i manually setted time of one server “equal” to that of the other with “date” command. This morning someone rebooted (it really was a black-out) the machines and in /var/log/messages of one machine i’ve noticed a 20 minutes lag back in time:

5:45 ..
5:49 ..
6:02 ..
shutdown
5:41 ..

And so i’ve remebered what i’ve already noticed with my test of RAC installation on VMWARE virtual machines
System Clock is not Hardware Clock. When linux boots, it sets system time equals to hardware time and then it may diverge. So the moral is; use hwclock

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4 Responses to “hwclock and date”

  1. Zahra Says:

    Hi,
    I am using the SUSE 10 server enterprise sp1. I have a problem with system clock. every time the server is shut down , after rebooting it the clock would be wrong!
    I set the clock on both UTC and local time but …
    if any one has an idea please help me!

  2. oracledb Says:

    Hi Zahra,
    how do you set your clock? do you use hwclock?

  3. Zahra Says:

    I set th the clock via os (time&date adjusting)
    the bios clock has been set correctly too!

  4. Siert Says:

    Fix time with the commands:

    ntpdate ntpserver.domainname.extension
    hwclock –systohc

    Also make sure /etc/ntp.conf is configured properly and the ntp daemon is enabled at runtime (chkconfig –list|grep ntpd)


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