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From Joerg von Frantzius <joerg.von.frantz...@artnology.com>
Subject Re: [DISCUSS} Server TimeZone
Date Fri, 09 Feb 2007 15:08:10 GMT
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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