[ntp:questions] ntpd executable -x option

unruh unruh at invalid.ca
Thu Apr 12 02:12:20 UTC 2012

On 2012-04-12, Nick G <nickgeovanis at gmail.com> wrote:
> On Wednesday, April 11, 2012 5:29:15 PM UTC-5, David Woolley wrote:
>> False.  It will continue to use the user space time discipline it has 
>> been using all along.  This has a one second sawtooth, so is not as 
>> accurate as the kernel space discipline, which applies corrections on 
>> every clock interrupt.  However, it will still apply the last known 
>> frequency correction.
> There is a "cluster verification" script-and-binaries which you use to make certain that your server has all it needs to run Oracle RAC (11.2.0 specifically). That tool tells me that I must run ntpd (good...) and I must run it with "-x" (ehh?). I'm failing to dream-up a good reason why Oracle RAC might want reduced time-keeping accuracy. Are they really looking for fewer "unnecessary" local clock corrections? Or a wider tolerable time-spread among the cluster members? Fewer "stolen" cycles in kernel mode?
> Thanks.....NickG

man ntpd

If the -x option is included on the command line, the
       clock will never be stepped and only slew corrections will be

Ie, it makes sure that the time is never stepped. stepping the time
might well be bad for a database (eg and entry that actually occured
befor another is recorded as occuring after). Mind you that should only
come into play on startup, or if the remote server comes back up after
being down a while. 

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