The primary tools for debugging errors in APPC/MVS TPs are described in Diagnosing Problems with APPC/MVS TPs, which includes a section that helps programmers decide which tool to select.

When APPC problems might involve the network or system configuration, system programmers can use APPC component trace to collect diagnostic information. Use the TRACE CT command to start APPC tracing and the IPCS CTRACE subcommand to format the trace data. See z/OS MVS Diagnosis: Reference for more information.

For conversations that cross the VTAM network, VTAM traces can help diagnose communications problems. See z/OS Communications Server: SNA Diagnosis Vol 1, Techniques and Procedures for more information.

The MVS and VTAM trace facilities can return detailed information about a conversation, including data that passed between the TPs. For example, the FMH-5 (Functional Management Header-5) contains the input for an inbound allocate request; APPC passes that input in the FMH-5 across the network to the partner LU. To understand the contents of an FMH-5, see SNA Formats.