Daylight Saving

[KeeHing Ng]

How UX handles daylight saving, what's the details behaviour like? Is this automatically handles by the system?
Appreciate any information on this. Thanks

Rgds
Kee

[Manju Kampli · Accepted solution]

The daylight saving of the system is based on Timezone variable set in the system. It refers to /usr/lib/tztab file and takes the necessary actions as specified in tztab file for each timezones.
This action is done internally with HP-UX, and does not require any manual date changing. How ever it is highly recommended to shutdown the applications like Oracle during time change for a proper application and data recovery incase of disaster.

[KeeHing Ng]

What's the detail of the action of daylight saving handles by HP-UX? If I have a OLTP application, will this action affects the time of each transaction?

[Andy Monks]

Any half decent application only logs times using UTC (or GMT). Then it applies the required TZ adjustment when it's displaying it to users. That way, daylight savings time will never cause a problem.

However, as I said this applies to 'half decent' applications. I'd check with your software vendor exactly what they do.

[Duane Gorder]

HP-UX keeps track of time in UTC (Coordinated Universal Time). When daylight savings time starts, the actual system time does not change. To convert time to local time, the system checks /usr/lib/tztab. I recommend taking a look at the file just to see what it looks like. It has the dates for when any individual time zone enters and leaves daylight savings time, and does the conversion for the computer when it is asked for local time. This also allows people in other time zones accessing the same computer over their WAN to use their own local time with the local $TZ variable. Check it out with a "man environ".

FYI we are an Oracle shop, and we don't worry about the time changeover because Oracle logs with the UTC time. We have never had a problem with HP-UX and Oracle, although our mainframe from a different vendor has to be shut down for an hour every fall to set time back

[Anthony Goonetilleke]

Also just a reminder to any aussies reading this thread, don't forget to apply the new daylight savings patch for this year as Daylight savings starts early due to the Sydney Olympics!