.NET Provider : Tracing

According to the (sparse) documentation setting these two Environment Variables will enable tracing: IFXDOTNETTRACE IFXDOTNETTRACEFILE Doesn't work. The reason I want to log a trace is that I'm executing a UDR that inserts some values into a table. The table contains non-nullable columns and I thought it would be a simple matter to catch any exceptions if the insertion of a null was attempted...but no. No exception is thrown. No event is raised. There's just a long delay before the IfxCommand instance returns a null value, very helpful. Anyone ever got the tracing (or any of this stuff!) to actually work as per the manual?!