>> Use MON$xxx tables and search for attachment of tx 1507. Look at application which
>> holds it and fix it to not hold transaction too long.
>
> The application name is a bit of a problem if the application does not
> use the Firebird client library from 2.1, e.g. when using Jaybird.
>
> Is there probably a way how Roman could make the application name
> available in the monitoring tables?
>
> Possibly, the same applies to the .NET data provider as well.

Of course. They need to specify isc_dpb_process_name in DPB.
Of course, if remote server is FB 2.1 or higher, i.e. supports protocol
version 11 or above.

Regards,
Vlad