Hi Dmitry,

I am not overly worried about supporting/maintaining this application, it is large, but it is after all just an application. SQL is SQL at the application level, it just happens to be Firebird. I was effectively being lazy, by looking for some quick way to isolate some of the problems by letting the database tell me what was wrong in the application, so I wouldn't have to debug this application in detail. Unfortunately, the problems we are experiencing are only visible when the system is under load, so it is tricky to simulate/emulate the environment. If we run a few users, we have no problems, so hence my questions about multi user transactions and isolation levels.

Thanks for all the assistance, to date.

Regards,
Sean

--- In firebird-support@yahoogroups.com, Dmitry Kuzmenko <kdv@...> wrote:
>
> Hello, sean!
>
> Thursday, March 28, 2013, 6:11:17 PM, you wrote:
>
> syc> We are not the original developer of the application,
>
> oops.
>
> syc> but have
> syc> now been given the task of maintaining/debugging this 750,000 + lines of Delphi 7 code.
>
> OMG.
>
> syc> Does FireBird support isolation levels ?
>
> yes, but if you are not familiar with Firebird, all this idea to
> maintain/debug that application seems impossible.
>
> syc> There are a number of
> syc> transactions that are waiting for locks to be release, which can be solved by changing the
> syc> isolation level to dirty/uncommitted reads. These are for read only transactions.
>
> really? multiversion architecture of Firebird allow to have lock
> conflicts only when 2 transactions update same record. There are no
> locks when you read data, at all.
>
> Of course, you may set special "isolation level", that will show locks
> on reading data, that is being modified, but this is not default, and
> you need to set these transaction parameters deliberately.
>
> And, with the new information about application, I can say that
> Firebird 2.5 trace/audit will not help you. Because trace helps only
> when you know, what happens inside application, i.e. how it works.
> If not, you cant compare what happens in Firebird, and what happens in
> application.
>
> You just need to check the exception handling in application, and at
> the first time find every place where exceptions are being kept back by
> the code.
>
> --
> Dmitry Kuzmenko, www.ib-aid.com
>