Use the CSM option on the VTAM® internal trace (VIT) or, when VTAM is not active, the GTF trace facility to obtain trace output of application requests to CSM.

When VTAM is operational, the CSM trace facility is controlled using VIT. CSM writes records to the VIT using VTAM trace interfaces. The CSM trace option controls the generation of CSM trace records for both internal and external tracing.

When VTAM is not operational, the VIT is not available and only external tracing is provided. The external trace is generated using the VTAM GTF event ID to write trace records directly to GTF in the same format as those recorded using VIT.

CSM tracing records the parameter list information that flows across the CSM interface and key internal events (such as pool expansion and contraction) for functions that manipulate buffer states. This allows you to trace and analyze the usage history of a buffer.

The number of trace records required to represent one IVTCSM request varies based on the number of buffer operations requested. Because the information required to trace one IVTCSM request can span several CSM trace records, you can use the trace record flag field to determine whether additional trace records exist for a particular IVTCSM request. If the first bit in the trace record flag field is set to on, the trace record is continued. If VIT is not active, multiple trace records for an IVTCSM request could be interspersed with trace records of IVTCSM requests from other users. A unique trace record number correlates the continuation trace records for each IVTCSM request.

For more information about tracing events over the CSM API, see z/OS Communications Server: SNA Diagnosis Vol 1, Techniques and Procedures.