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Re: TAF and FCF together ?

From: <joeNOSPAM_at_BEA.com>
Date: 16 Sep 2006 08:06:29 -0700
Message-ID: <1158419189.600230.260770@i42g2000cwa.googlegroups.com>

DA Morgan wrote:
> joeNOSPAM_at_BEA.com wrote:
>
> >> With a TAF failover the query restarts with the same SCN. Thus the
> >> result set is exactly the same.
> >> --
> >> Daniel Morgan
> >> University of Washington
> >> Puget Sound Oracle Users Group
> >
> > Sorry, my newsreader sometimes makes it very difficult
> > to bottom post!
> >
> > My concern is that the SCN does not necessarily indicate the
> > same DBMS datum from DBMS to DBMS over time, for instance
> > if the table has changed between the failure of a connection and a
> > eventual reconnect to the other DBMS.
>
> Of course it does. That is precisely what Oracle's Multiversion
> Consistency model is all about. This is Oracle Concepts and
> Architecture 101. Oracle uses the SCN, which equates with a timestamp,
> and the rollback/undo to reconstruct the data as it was at specific
> moment in time.
>
> There are members of your team working with RAC here in the Puget Sound
> region, perhaps you are one of them, if so you might want to contact me
> off line. At least one member of your team took my class at the U and
> it seems there are quite a few misunderstandings on the part of BEA
> about RAC.
>
> > The oracle TAF document
> > warns that on occasion, a query will fail, and I was interested
> > in expanding the example to actually exercise TAF's requery ability,
> > and wondering if these failures are always obvious.
>
> Run the demo downloadable from the PSOUG website. That is precisely
> what it reports and precisely what we use it to demonstrate.
>
> Look in the code following the comment that begins:
> * There are 7 possible failover event
>
> > I think we both agree that TAF is being deprecated, but there are
> > some, obviously that are still being lured by the siren-call of it's
> > promise.
>
> Hardly a siren call. It is a valuable technology not available from
> any other RDBMS vendor. The only reason I prefer FCF is its relationship
> with FAN and the fact that it works as well with SQL*Plus as with OCI,
> or Java thick or think or, .NET.
>
> > If we expanded the example to more thoroughly test
> > TAF, and if it exposed more of the Oracle-documented problems,
> > it might serve to sway these tempted souls from the rocks or
> > show how to handle them.
> >
> > Joe
>
> Perhaps I am mistaken but you don't need an expanded example. You
> just need to understand, far better, the one you have already.
> --
> Daniel Morgan
> University of Washington
> Puget Sound Oracle Users Group

Alright, thanks, I'll work on it.
Joe Received on Sat Sep 16 2006 - 10:06:29 CDT

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