I have found tracing to be very useful when troubleshooting problems. Tracing (or session-based logging) lets you activate detailed logging for specific customers. The system I worked on processed SMS messages for mobiles. There you could enable tracing on a specific mobile phone number, and whenever that subscriber sent an SMS, you got more detailed logs for everything affecting that SMS. Really a great tool. I've described it in more detail here: http://henrikwarne.com/2014/01/21/session-based-logging/