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Radu Curca · Guest

We have a three tiered application.
The middle tier is a MIDAS/Datasnap COM+ application which connects to
Interbase/Firebird through BDE.

The COM+ object use a MtsDatamodule which contain a TDatabase component. We
do not use TSession components. When the middle tier application receives
many requests from clients during some load tests (especially when
ApplyUpdates execute very fast) we get the error: "A user transaction
already in progress" error appears. The error appears randomly;

The COM+ application/app server was anhanced to work in multithreaded
envoronment, and we used a standard & recommended solution. A TSession
component was added.
The error "A user transaction already in progress" DOES NOT appear anymore.
Instead, again randomly, the
"Error reading from the connection"/"Error writing to the connection"
appears now.

Some tests peformed on a simple database components - no COM+ app servers -
Showed that "A user transaction already in progress" error appears when
trying to start a transaction on a TDatabase component which is already in
transaction.
"Error writing to the connection" appears when 2 distinct threads try to
access the same connection to IB at the same moment.

Is there a cause for all these error messages?