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From Erik Bengtson <e...@jpox.org>
Subject Re: [DISCUSS} Server TimeZone
Date Fri, 09 Feb 2007 14:51:10 GMT
I don't think the spec prohibits multiple dbs in the backend, so my
concern is to not difficult it

Quoting Joerg von Frantzius <joerg.von.frantzius@artnology.com>:

> Hello Erik,
>
> this seems to be connected to thread Transaction Manager and JCA
> <http://www.jpox.org/servlet/forum/viewthread?thread=4099>, where it
> seems you proposed to associate a single PersistenceManagerFactory with
> multiple DBs. As a PMF only has properties to connect and authenticate
> with a single DB (URL, username/pw), I think the spec implicitly defines
> that a PMF can be connected to a single DB only.
>
> So it seems to me your question implies some fundamental conceptual change?
>
> Regards,
> Jörg
>
> Erik Bengtson wrote:
> > Craig, I understand that server means the backend database server. what it
> we
> > have multiple backend db servers?
> >
> > Use case with multiple dbs:
> >
> > SELECT FROM db1.classA WHERE classA.time > datetime() && classB.time
>
> > datetime() VARIABLES db2.classB
> >
> > The first datetime() is evaluated by db1, while the second by db2.
> >
> > Quoting Craig L Russell <Craig.Russell@Sun.COM>:
> >
> >
> >> Here is a proposal to add the ability of a user to get the time at
> >> the server in a portable way.
> >>
> >> This should allow an application to avoid time skew by using the time
> >> as seen by a single source, the server to which the
> >> PersistenceManagerFactory is connected.
> >>
> >> <proposed>
> >> 11.1
> >> ...
> >> ServerTimeZoneID: the time zone ID of the server to which this
> >> PersistenceManagerFactory is connected, for use with the
> >> PersistenceManager method getServerDate
> >> If ServerTimeZoneID is specified, the value must correspond to a
> >> valid time zone ID as returned by TimeZone.getAvailableIDs(). The
> >> implementation uses the ServerTimeZoneID to implement the
> >> getServerDate method. If ServerTimeZoneID is not specified, the
> >> implementation might use proprietary methods to determine the time
> >> zone in which the server is located. If ServerTimeZoneID is not
> >> specified, and the implementation cannot or does not use proprietary
> >> methods to determine the server time zone, then the default time zone
> >> ID of the Java VM is used.
> >>
> >> 12.17 Server Date
> >> java.util.Date getServerDate();
> >>
> >> Time skew is a phenomenon in which machines connected together in
> >> client/server configurations might have clocks that are not perfectly
> >> synchronized, and the time as seen by different clients might differ.
> >> In order for the application to avoid time skew, this method can be
> >> used to acquire a Date instance corresponding to the UTC Date as seen
> >> by the server. Clients using this method can order their operations
> >> according to a single time source.
> >> Implementations use the setting of the server time zone to prepare a
> >> Date instance that represents UTC time on the server.
> >> </proposed>
> >>
> >> Craig Russell
> >> Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
> >> 408 276-5638 mailto:Craig.Russell@sun.com
> >> P.S. A good JDO? O, Gasp!
> >>
> >>
> >>
> >
> >
> >
> >
> >
> >
>
>




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