LU2 and non-SNA 3270 screen size and model information

After the Logon exit routine approves the logon, BIND image data (screen-size) and feature information from the logon descriptor are used to search the MFS device characteristics table for the appropriate MFS device information.

If the model is specified in the screen size control byte the MFS device characteristics table is not searched. A DFS3646 error message is issued if no match exists on screen-size and feature. The information from the proper MFS device characteristics table entry is then used for that device. This information in the MFS device characteristics table comes from the IMS system definition or the MFSDCT utility (DFSUTB00).

If the screen-size control byte is X'7F' and both the default and alternate screen-sizes are specified, a search of the MFS device characteristics table using alternate screen size commences. If no match is found, another search begins using the default screen size. If no screen size is found, message DFS3646I is issued to the operator.

The screen size (the product of the lines and columns) must be in the range 80-16384. The lines and columns must each be in the range 1-255.

If the screen size and features of the 3270 device that is logging on maps into two or more MFS device characteristics table entries, the first entry in the table that matches the screen size and features is selected.

If the screen-size control byte (the 11th byte of the PSERVIC on the VTAM® MODEENT) is X'00' and both default and alternate screen-sizes are specified, a search of the MFS device characteristics table using the default screen-size occurs. If no match is found, another search begins using the alternate screen-size.

Use the Logon exit routine, DFSLGNX0, to override the screen-size or model for the device during logon.