Oracle internals, debugging and undocumented features

Network Time Protocol ( NTP ) & Clusterware diagnostic script

One of the prerequisites to successfully install  Oracle version 11.2 is to set Network Time Protocol ( NTP )

( file /etc/sysconfig/ntpd )

with -x flag which prevents time from adjusting backward.

This comes very crucial in debugging Oracle Clusterware.NTP will synchronize clocks among all nodes which will make correct analysis of trace files based on time stamps .

Oracle is providing diagnostic collection script diagcollection.pl to collect important log files.

Script is located under  $<GRID_HOME>/bin/ e.g.  /u01/app/11.2.0/grid/bin

It will generate four tar.gz files in local directory which will have following information:

traces,logs and cores for CRS home

ocrcheck , ocrdump

CRS core files

OS logs

After you are done you can clean them with same script.Just run diagcollection.pl -clean option.

Script must be run as root .

3 responses to “Network Time Protocol ( NTP ) & Clusterware diagnostic script

  1. jarneil December 10, 2010 at 4:02 am

    Hi Mladin,

    I’ve seen the “-x flag which prevents time from adjusting backward.” Printed in the Oracle documentation as well, but that does not seem to square with the man page of ntpd:


    This would seem to indicate that it has nothing to do with the direction of time adjustment.


  2. oraclue December 10, 2010 at 5:01 pm

    Hi Jarneil,

    You mean this?

    As the result of this behavior, once the clock has been set, it very rarely strays more than 128 ms, even under extreme cases of network path congestion and jitter. Sometimes, in particular when ntpd is first started, the error might exceed 128 ms. This may on occasion cause the clock to be set backwards if the local clock time is more than 128 s in the future relative to the server. In some applications, this behavior may be unacceptable. If the -x option is included on the command line, the clock will never be stepped and only slew corrections will be used.

  3. jarneil December 11, 2010 at 2:53 am

    Hi Miladin,

    I’m still confused, but maybe it’s my lack of understanding of the difference between “stepped” and “slewed”. I’m thinking you are saying stepped would mean it actually moves the clock backwards, so what actually happens with slewed?

    If you have a server that is ahead of the ntp server, how does being “slewed” actually get you back to the correct time?


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