Selecting the autoinstall model

If you are using model terminal support to supply the model name (and the named model exists and is valid), CICS® passes the model name to your autoinstall control program—you do not need to make any further selection.

As a general rule, all the models in the list passed to your program match the SNA data for the LU. That is, a viable TCT entry usually results from the use of any of the models. (The exception to this rule involves the z/OS Communications Server for SNA RUSIZE; if this value is incompatible, CICS issues an error message.) The default autoinstall control program merely picks the first model in the list. However, this model may not provide the attributes required in all cases. For instance, you do not want a 3270 display device definition for a 3270 printer. Your control program must be able to select the model that provides the characteristics you require for this terminal—for example, security characteristics.

To save on storage, you should try to minimize the number of different models available to the control program, and the number of different TYPETERM definitions referenced by those models. If you are migrating your definitions from DFHTCT macros, look carefully at them and eliminate those that are unnecessarily different from others. Use the QUERY function for all devices that can support it. For bisynchronous devices, which do not support QUERY, one approach is to make the definition as straightforward as possible, with no special features.

If you need special models for special cases, you can use a simple mapping of, for example, NETNAME (generic or specific) to AUTINSTNAME. Your control program could go through a table of special case NETNAMEs, choosing the specified model for each. The default model would be used for any terminal not in the table. The list of models presented to the control program is in alphabetical order with one exception, which is described in the notes to z/OS Communications Server MODEENT macro operands.