Thank you for the idea but this is not what I'm looking for.

I think that inserting same record twice must produce error and not to to block the execution of other connections.

So in this case I'm trying to find where the problem is exactly.

This table is having problem with only one installation.

Another installation is having problem with another table.

I really don't think is a good idea to make changes to the logic that works perfectly on 20 other installations just because I have problem that is not in the logic with only one installation.

Is there any way to look in the firebird process where it is stuck?

I'll try to extract stack trace from java side.