In the distributed processing environment, debugging programming errors is much like solving a complicated murder mystery; your goal is to find out what killed your TP. Fortunately, APPC/MVS provides the following diagnostic tools to help you solve that mystery:

• The API trace facility,
• The Error_Extract callable service, and
• The TP message log.

These tools differ in several ways that can help you determine which tool, or combination of tools, is best suited to detect the cause of the error. The following topics describe these differences in general terms; for detailed information about each tool, see:

• Diagnosing TP Conversation Errors with the API Trace Facility
• Overview of Error_Extract Service
• The section on logging TP processing in z/OS MVS Planning: APPC/MVS Management.