Re: DST Changes

From: Kumar, Praveen (cahoot) (Praveen.Kumar@CAHOOT.COM)
Date: Wed Feb 25 2004 - 13:58:44 EST


Simon,
        Thanks for the response!!The issue here is that DST is not set to
on,so currently we are doing a manual time change,so in such scenarios are
there any special issues to be taken care. or is it just stop all your
applications and set the time back/forward as applicable.

TIA
Praveen.K

-----Original Message-----
From: Green, Simon [mailto:Simon.Green@EU.ALTRIA.COM]
Sent: 25 February 2004 17:19
To: aix-l@Princeton.EDU
Subject: Re: DST Changes

Provided your Timezone is set correctly, (TZ in /etc/environment) there
should not be any problem and there is no need to take any further action.
It's worth remembering that ideally you should re-boot your system if you
have to make a change to TZ, but it's not always strictly necessary: I made
a lot of changes recently and all I've done is restart the cron daemon and
ensure that the applications, (mostly SAP and Data Warehouse systems) are
re-started - not actually a full reboot of the systems.

Any half-way decent application will use the actual system clock for
critical things like database log timestamps, so there is no problem there.

It's possible that you'll see overlapping time-stamps in text logs, but that
won't do any harm in itself. Technical personnel should be aware of it.

Scheduling - through crontab or actual scheduling packages - may have some
issues, with jobs getting missed in the spring, or running twice in the
autumn. However, that's highly dependent on the particular scheduling
system. Crontab's very basic, obviously, but a good scheduler should handle
the situation cleanly.

Personally, I haven't taken any special actions for DST in several years.
We did have some problems last autumn because TZ was not identical on all of
our servers, in particular there were difference between some SAP
Application servers and their Database servers. This arose because of
differences in when the time change occurred:-

Some of the servers had TZ=CET-1CEST,M3.5.0/02,M10.5.0/03, others only had
CET-1CEST,M3.5.0,M10.5.0. In the second case, the time for the change
defaults to the US standard, which is 2am local time in both cases. In
Europe, the standard is for 01:00 GMT, which equates to 02:00 CET in the
spring, or 03:00 CET in the autumn.

In fact, this doesn't really matter very much in most cases, provided you
are consistent.

The correct TZ for the UK is "GMT0BST,M3.5.0/01,M10.5.0/02". You can either
edit /etc/environment, or use the chtz command.

--
Simon Green
Altria ITSC Europe Ltd
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> -----Original Message-----
> From: Kumar, Praveen (cahoot) [mailto:Praveen.Kumar@CAHOOT.COM]
> Sent: 25 February 2004 16:32
> To: aix-l@Princeton.EDU
> Subject: DST Changes
>
>
> Hi All,
>
>         Can someone let me know what are the issues to be
> taken care during
> DayLight Saving Time changes. My aix boxes have Websphere and
> HTTP Server
> running on them..
.sophos.3.78d.02.24.
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