An interesting problem was presented today, when a database system was presented that was raising, seemingly intermittently, unhandled exceptions within a particular section of the system. This would have been a pretty tractable, but for the fact that the source code was not immediately available and the problem was on a live system and so needed to resolved with some urgency.
Admittedly, there was some initial head scratching while table records were examined and compared to try and identify any inconsistencies. This revealed nothing and the JIT debugger could not be enabled as the exceptions were being raised in a windows form that had not been compiled to allow JIT debugging.
The next approach was to see if the SQL commands the client was executing could be intercepted. Then, the thinking went, the commands could be compared to see what was going wrong and what was going right when exceptions were and were not raised. As it turned out SQL Server provide a tool called a Profiler that offers this functionality but this is not provided with the version we were working with - SQL Server 2005 Workgroup Edition. However we did find this open source Profiler with which the cause of the problems was identified. Such profilers are more commonly used to monitor database server workloads.