On Jan 27, 2006, at 9:14 AM, Roman Rokytskyy wrote:

>> Thanks for the reply. Yes, the test case provided does work with
>> CONSISTENCY, but my test case with 2 threads now results in a
>> deadlock,
>> even though I use WAIT, when I change to CONSISTENCY.
>
> Which is more or less how it is supposed to behave - it generates you
> message about deadlock on transaction start. You can then wait and
> restart
> it... I would however expect it to wait until it gets the lock, but
> I'm not
> sure if that is designed so...
>
>> The reason I used CONCURRENCY was due to reading the Helen
>> Borrie's The
>> Firebird Book pg 526 & 527: "using table reservation with
>> SNAPSHOT or
>> READ
>> COMMITTED isolation is recommended in preference to using SNAPSHOT
>> TABLE
>> STABILITY when table-level locking is requuired....using it in
>> combination
>> with SNAPSHOT TABLE STABILITY is not recommended".
>
> Ok, I'm sure Helen knows more...
>
>> My understanding is that isc_tpb_concurrency corresponds to
>> SNAPSHOT, and
>> isc_tpb_consistency corresponds to SNAPSHOT TABLE STABILITY?
>
> Right.
>
>> The book recommends RESERVATION because it locks all rows
>> pessimistically
>> at the beginning of the transaction, rather than when first
>> accessed by a
>> statement. This goes back to my earlier question - how do I start a
>> Transaction before issuing a statement using Jaybird?
>
> Only by executing some dummy statement, for example "SELECT * FROM
> rdb$database".

won't running in an app server using JTA transactions result in the
tx starting when the JTA transaction starts and the connection is
assigned to the thread, whichever occurs second?

thanks
david jencks

>
>> I am sure you're very busy, but would you have a minute to run the
>> attached threaded testcase, or can you see why a deadlock would be
>> the
>> result even if I am using WAIT?
>
> Yup, it is quite surprising...
>
>> I would greatly appreciate it. As you
>> can tell, I'm fairly new to all this!
>
> Me too :) Only that I coded that part...
>
> Roman
>
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