Dne 10.1.2011 19:03, Ann W. Harrison napsal(a):

> On 1/10/2011 2:53 AM, Milan Tomeš - Position wrote:
>> I've run into problems with deadlocks.
>> In my application I'm running multiple threads where every thread runs
>> against different target database (but against same server). In that
>> thread a single command is executed (update in this case) in a single
>> transaction. Sometimes - totally randomly - command or server crashes
>> with "deadlock" error and I'm really confused why this happen. If I
>> restart that command against same database it finishes sometimes
>> correctly and sometimes crashes again.
>> Can anybody help me?
> Probably, but it's going to take some effort on the part of several
> people. With very high probability, you're running into an internal
> server deadlock, which is not supposed to happen. The first thing
> you'll need to provide is the exact text of the error message, and
> if possible, some indication of what was happening on the system
> when the error occurred.
>
> User-data deadlocks occur when concurrent transactions attempt to
> update or delete the same record. They are of two types. The first
> is called an update conflict and is normally reported when one
> transaction commits after updating or deleting a record that a
> concurrent transactions has tried to update or delete. The second
> is a classic deadlock: one transaction updates or deletes record
> A then attempts to update or delete B; a second transaction updates
> or deletes B then attempts to update or delete A. Firebird cannot
> prevent user level deadlocks, but it does detect them and returns
> errors that allow the application to break the deadlock. Since
> every thread in your application runs on a different database, you
> can't be updating the same record in several transactions.
>
> System deadlocks occur when threads within the Firebird process
> conflict on access to internal structures. In theory, Firebird's
> design avoids or corrects those deadlocks automatically. In your
> case, that appears not to work. The easiest solution might be to
> use Classic mode, which will give you a process for each database.
> That might be more efficient, in addition to not deadlocking. The
> super classic version of 2.5 might also help.
>
> However, if you can supply enough information to let the developers
> find the problems you're seeing, they will be able to improve
> Firebird for everyone.
>
> Best regards,
>
> Ann

Hello Ann,

in case of deadlock I get a "deadlock" error message in Firebird's log
file but in application everything seems to be OK (except, that Firebird
doing nothing). So I guess that I'm getting internal server deadlock. If
you can write me what type of information I can send you, I'll do my
best to do it.

Milan