DST patch - Libraries

[brian_31]

I know there is no reboot required for the DST patch on HP-UX. we have a mixed platform and some senior platform architacts are suggesting that we reboot the HP-UX boxes like the solaris boxes so that the application come up cleanly. I think they are suggesting this from their solaris experience as solaris has a different way of patching (it updates some libraries also) which the applications wont use until they reboot them. for HP-UX though, it is only tztab..i know it does not hurt anything by rebooting. but my take was it was not required absolutely for the DST patch. is that correct?

Thanks

Brian

[James R. Ferguson]

Hi Brian:

The application of the DST patches on HP-UX does not require a reboot. However, at least the 'cron' daemon and other long-running processes should be restarted in order for the libc routines to cache the new rules by re-reading the '/usr/lib/tzlib' file. If you are absolutely sure that restarting 'cron' and (notably) your databases covers all processes, then so be it. Otherwise, a reboot sometime before the daylight transition is my preference.

Regards!

...JRF...

[Peter Godron]

Brian,
you are correct, no reboot required.
Any session connected after the DST will pick up the new data. See http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=993053

But, unless you need 24/7 availability, what is the harm of rebooting.

[A. Clay Stephenson]

As has already been pointed out, the "gotcha" (other than needing to restart the cron daemon) are those long-running processes which have already read their corresponding tztab entries. They will not have a clue that tztab has changed. Once upon a time, tztab was read each and every time one of the ctime functions such as localtime() was called (to avoid your problem) but that caused performance problems --- especially since tztab changes are so infrequent. A later patch then decided to cache the tztab entry so that once read, there was no need for the same process to reread the file. Unless you are intimately familiar with all the long-running applications on your box, you would be wise to schedule a reboot.