Defining TSO/VTAM session parameters

VTAM® needs to know the session protocols required by the terminals from which individual TSO users log on. This information is provided through logon mode tables and through VTAM and NCP definition statements.

Logon mode tables associate session protocols with device types. IBM® provides a default logon mode table that describes session protocols for common devices and situations. However, you might need to replace or supplement the default table.

In addition, a specific Class of Service name can be chosen. The Class of Service name used for the session is selected from the logon mode entry. If you omit the COS operand on the MODEENT macroinstruction, the default COS is chosen. To choose a specific COS, you need to include the COS name on the MODEENT macroinstruction as follows:

MODEENT  COS=cos name,logon mode parameters

The connection between a logon mode entry and a device is made using VTAM operands on the LU, LOCAL, or TERMINAL definition statements during VTAM and NCP definition. Code the DLOGMOD operand to identify the name of a logon mode table entry containing the session parameters used for the 3270 device being defined. Code the optional MODETAB operand to identify the logon mode table containing the entry. If you do not code MODETAB, the IBM-supplied logon mode table (ISTINCLM) is used.

You can also code the MODETAB and DLOGMOD operands on the GROUP, LINE, PU, LU, or CLUSTER definition statements to take advantage of the sift-down effect.