A logon mode name is used to suggest a particular set of session parameters and class of service (COS) that is used between session partners. The logon mode name can be specified by one of the session partners or the VTAM® operator at different points in the session-initiation and session-establishment process. Table 1 shows how a logon mode name can be specified.

The following steps describe how a logon mode name is used:

1. The logon mode name is supplied by a session partner or operator as part of an Initiate request.
2. The VTAM that owns the SLU maps the logon mode name in the logon mode table and translates it into session parameters and a COS name.
3. If necessary, the logon mode name is passed from the domain in which the Initiate request originates to the domain of the VTAM that owns the SLU and is then translated in that domain. If no logon mode name is supplied as part of the Initiate request, the appropriate default session parameters and COS name are determined in the VTAM that owns the SLU.
   Note: If the logon mode name supplied as part of the intitate request cannot be translated in the VTAM that owns the SLU, VTAM might use the default logon mode entry ISTCOSDF. For additional information regarding the ISTCOSDF start option, refer to z/OS Communications Server: SNA Resource Definition Reference.

   For the OPNDST macroinstruction, the COS is not specified in this field (because it is associated with a queued CINIT that cannot be overridden) unless it is an OPNDST OPTCD=ACQUIRE operation.

4. The session parameters and COS name are then passed to the VTAM that owns the PLU. VTAM uses the COS name to determine a set of COS parameters.
5. The session parameters and COS parameters are sent to the PLU in the CINIT.