Timing: When Tracing Starts

In Figure 1, if TPB allocates a conversation with its partner TPA (1a) before you issue the START request (2), APPC/MVS does not provide any trace data for that conversation, even though the LU and TP values match. APPC/MVS provides trace data only for conversations that are established after it finishes processing a START request.

Generally speaking, a conversation is established when a program issues an Allocate call or, in the case of APPC/MVS servers, a Register_for_Allocates call. When the ATBTRACE START request is issued before the conversation is established, trace data begins with a trace entry for the Allocate or Register_for_Allocates call.

For APPC/MVS TPs that issue CPI-C verbs, however, a conversation is established when either:

The TP issues CMINIT, specifying a valid symbolic destination name. In this case, trace data begins with a trace entry for the CMINIT call.
The TP issues the last CPI-C call to set either the partner LU name (CMSPLN) or TP name (CMSTPN). For example, suppose the TP issues the following calls in sequence:
1. CMINIT, without specifying a symbolic destination name
2. CMSPLN, to set the partner LU name
3. CMSTPN, to set the TP name.
In this case, trace activity begins with the CMSTPN call.

In Figure 1, because TPD does not reside on MVS01, the only trace entry for TPD's side of the conversation is an FMH-5 received at LUA from OSLUA (3a). If TPD did reside on MVS01, trace data would include an ATB60055I message for the CMSTPN call, and messages for subsequent calls by TPD.

Figure 1. Timing the Start of API Tracing Activity

APPC/MVS does not start tracing activity at all for the LU/TP combination, if the call to establish the conversation contains partner LU name or TP name values that do not match the LU/TP combination specified through the ATBTRACE START request.