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From Erik Bengtson <e...@jpox.org>
Subject Re: [DISCUSS} Server TimeZone
Date Fri, 09 Feb 2007 16:18:24 GMT
Joerg,

> How do you want to configure multiple database connections per PMF
> without extending the spec?

Agreed, this has to discussed/specified in JPOX. After completed the
implementation, I see this as a potential feature to be proposed to JDO
standard

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

> Erik Bengtson wrote:
> > I don't think the spec prohibits multiple dbs in the backend, so my
> > concern is to not difficult it
> >
> The spec allows for multiple DBs in the backend, with a single PMF for
> each of them (or what backend were you referring to?)
>
> How do you want to configure multiple database connections per PMF
> without extending the spec?
> > 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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