Re: how does Oracle handle changes to system time of day

From: GUY R. LOUCKS <loucksg_at_engsyd.bhp.com.au>
Date: 9 Jun 94 18:18:59 EST
Message-ID: <1994Jun9.181859.1_at_engsyd.bhp.com.au>


In article <Cr0D53.FKy_at_cmutual.com.au>, aaj_at_cmutual.com.au (Tony Jambu) writes:
>
> Sundar
>
> In article <2sp761INNao1_at_life.ai.mit.edu>, sundar_at_ai.mit.edu (Sundar Narasimhan)
> writes:

>> Hi, I'd like to know how people keep correct time on 
>> their machines running Oracle. (i.e. programs like
>> rdate end up changing the time of day clock on Unix machines).
>> I've been hearing that bad things can happen to a continuously running
>> Oracle database if one uses programs like rdate or timed. So
>> what is the right solution?

>
> A similar question was put to Oracle about a year and a half ago. It was to
> do with daylight saving. Basically, bad luck if you need to
> recover your database using archive logs in the one hour that was put back in
> time. Putting the time forward is OK, setting it back is a problem.
>
> This problem exist for all other types of programs/applications that is time
> dependent not just Oracle's.

>

Actually you can work around it on most mini/mainframe systems. The trick is not to just change the clook, instead use a program to slew the clock. This routine will ajust the internal system tick's used to calculate time making the clock (appear) faster or slower to the outside world.

I have used these programs on VMS based machines, and several UNIX variants. The VMS on VAX and ALPHA's both work the same, and most unix systems use a standard time subroutine.

If you are using a PC I think you have to give up, however MAC users can use the same technique.

Hope this helps,

Guy R. Loucks
DBA //## Standard Disclaimers ##\\ Received on Fri Jun 10 1994 - 01:18:59 CEST

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