Hi Juan.
----- Original Message -----
From: "Juan Lorandi (Chile)" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, January 30, 2001 10:48 PM
> really? I'm much afraid that within a given instance of orion, no more
than
> one instance of any given entity will map to a DB
> row. Of course, in a clustered environment with N machines, you'll have at
> most N instances of a given entity, in which case your assertions are true
> Carlos.
Yes that is my opinion. Anyway I don´t think this makes the difference for
the question.
Moreover, I´m not sure J2EE specs prevents a single server from having 2
instances of the same EB over the same row. It could be useful with high
concurrency. Remember that EB methods are synchronized.
> Isolation in transactions has many different variants or levels; check out
> orion-ejb-jar.xml for more details.
Of course you have alternatives. It´s up to you to select the good one for
your case.
> A select for update is only valid while you still reference the involved
> records, i.e.: is valid in this sequence
>
> (CONNECT)
> SELECT FOR UPDATE
> UPDATE
> [COMMIT]
> (DISCONNECT)
>
> however with ejb's:
> (CONNECT)
> SELECT
> (DISCONNECT)
> ...
> (CONNECT)
> [SELECT [FOR UPDATE]]
> UPDATE
> [COMMIT]
> (DISCONNECT)
>
> transaction context and transaction activity are key concepts in
> understanding what is really happening behind the scenes
>
> My 2c,
>
> JP
I´m lost. I´m not sure what you mean by "..."
Could you explain please. I´m very interested if this is a case where
transactional approach fails.
Thank you Juan.
> > -----Original Message-----
> > From: Carlos Otero Barros [mailto:[EMAIL PROTECTED]]
> > Sent: Martes, 30 de Enero de 2001 18:19
> > To: [EMAIL PROTECTED]
> > Subject:
> >
> >
> > Hi.
> > Not sure what you mean by "SELECT FOR UPDATE".
> > Two instances of the same Entity Bean over the same row still
> > have different
> > transaction contexts.
> > You may expect isolation from transactions so you can rely on them.
> > If two users try to update the row almost at the same time
> > from different
> > instances of the same class of Entity Bean then the standard
> > transaction
> > approach applies.
> >
> > Regards.
> >
> > ----- Original Message -----
> > From: "manishi tuli" <[EMAIL PROTECTED]>
> > To: <[EMAIL PROTECTED]>
> > Sent: Tuesday, January 30, 2001 7:53 PM
> >
> >
> > > if 2 instances of ejb are trying to update same row , can
> > we handle this
> > > thing with ejb transaction or we have to do with select for update
> > >
> > > thanks
> > >
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>
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