IDS Forum

Re: multiple timezone support

Posted By: Jonathan Leffler
Date: Tuesday, 17 May 2005, at 4:26 p.m.

In Response To: multiple timezone support (DAVID FORTUNE)

"DAVID FORTUNE" <david.fortune@ingenico.co.uk> wrote on 05/17/2005
11:09:44 AM:
> We currently have a 9.40FC4 instance running on Solaris 9 set to
GMTtimezone.
>
> My company is looking to host a copy of our database but running
> within Eastern Standard Time i.e 5 hour behind the UK. We do not
> want to customise the application so handle timezone adjustments.
>
> Is is possible to have 2 IDS instances on the same server but
> configured so that dates and times on the other instance are within
> another timezone?
>
> I have been looking at Solaris 10 "containers" as another option but
> am not sure whether that supports multiple timezones either.
>
> Any advice would be appreciated.

Be careful.

Yes - it's trivial to do, at least in principle. You do, however, have to
be very, very careful!

The trivial answer is that you start each server with the appropriate
value of TZ set in the environment of the server when it is started.

Presumably, this would be TZ=GMT0BST (or some more complex value which
tells the system when the time zone switches from GMT (aka UTC) to BST
because the rules are different in the USA from in Europe, even before the
US Congress adds a month to either end of Daylight Saving Time), and
TZ=EST5EDT. Personally, my systems all run with TZ=UTC0 - no switch
between winter and summer time.

The hard parts are (a) understanding what this does, and (b) making sure
it happens totally consistently.

a. The server evaluates CURRENT in the context of its time zone.
Regardless of the value set by the client and sent to the server at
connect time, the server uses its own TZ value when evaluating CURRENT. It
indirectly affects TODAY, too - the date boundaries are determined by the
server time zone.

b. My session from the IBM Data Management Technical Conference last year
'G08: Is Your DBA Paranoid Enough?', aka 'The Paranoid DBA', shows how to
ensure that your server is started uniformly. You should be able to find
the presentation at various local IUG web sites, hosted by the IIUG at
http://www.iiug.org/ - I've given it to user groups in Southern
California, Kansas, and Seattle (Seattle is most recent, and hence most up
to date - and also by far the longest; the presentation, in all versions,
has extensive 'speaker notes' which provide a lot of information).
Fundamentally, you have a single script that is always used to start each
server, and that script always set the entire environment to a known
value. This prevents your system administrators in Singapore or
California from screwing up your users in New York or London by
accidentally setting the server time zone to Pacific time or Singapore
time.

You do not need Solaris 10 zones to achieve this - and would be well
advised to stay clear of them (Solaris 10 zones) until we've certified
that IDS will work with them. There are a number of system calls that
processes running in a zone are not allowed to make, and IDS makes some of
those calls - caveat lector.

Note that if you have people working in California as well as New York (or
anywhere else in the US/Eastern time zone) and accessing the same
database, you will need to worry about time zones.

--
Jonathan Leffler (jleffler@us.ibm.com)
STSM, Informix Database Engineering, IBM Information Management Division
4100 Bohannon Drive, Menlo Park, CA 94025
Tel: +1 650-926-6921 Tie-Line: 630-6921
"I don't suffer from insanity; I enjoy every minute of it!"

Messages In This Thread

• multiple timezone support
  DAVID FORTUNE -- Tuesday, 17 May 2005, at 2:09 p.m.
  • Re: multiple timezone support
    Jonathan Leffler -- Tuesday, 17 May 2005, at 4:26 p.m.

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