VTAM's support for LU 6.2 does not allow a blank name to be specified as a value on the LOGMODE keyword. For example, if the application issues an APPCCMD CONTROL=OPRCNTL, QUALIFY=CNOS and the LOGMODE value is blanks, the macroinstruction will fail with an RCPRI,RCSEC of X'002C',X'0001' PARAMETER_ERROR_INVALID_MODE.

After a successful CNOS negotiation, the application might attempt to allocate a conversation with the partner using the name and mode just negotiated. If this occurs, VTAM® will internally issue the equivalent on the SIMLOGON macroinstruction to start the session for the conversation to use. If the logmode name specified on the APPCCMD CONTROL=ALLOC, QUALIFY=ALLOCD and subsequently used on the SIMLOGON is not defined¹ with the VTAM that owns the secondary logical unit (SLU), the SIMLOGON fails with a SNA sense code of X'08210002'. However, when VTAM receives this sense code, it reissues the internal version of the SIMLOGON with a logmode of blanks. When this macroinstruction completes with the default logmode values in the session initiation information (for example, the BIND image in the CINIT) then VTAM's support for LU 6.2 alters these values as specified in Table 2.

To summarize, after a successful CNOS, VTAM successfully activates the session even if the VTAM that owns the SLU does not contain a definition for the logmode name specified.