Building the device characteristics table

When someone logs onto an ETO 3270 or SLU-2 terminal that is connected to IMS, usually the screen size is provided to IMS in the VTAM® CINIT PSERVIC data. Sometimes the model number is also provided.

IMS uses this screen size and the features that are specified on the logon descriptor in order to search the MFS device characteristics table, which contains one or more entries. Each entry identifies the following:
  • The MFS device type
  • The screen size
  • The features

Searching the table, you can find the MFS device type. If the search is unsuccessful, the logon attempt is rejected, and messages DFS3646I and DFS3672I are issued.

The MFS device characteristics table is built in one of two ways:
  • The IMS system definition process builds an MFS device characteristics table based on the TYPE=, SIZE=, and FEATURE= specifications of the TERMINAL macro. Each unique combination has an entry in the MFS device characteristics table.
  • The MFSDCT utility (DFSUTB00) builds or modifies an MFS device characteristics table based on the input of the MFS device descriptor. These descriptors have the TYPE=, SIZE=, and FEATURE= specifications that the TERMINAL macro has. When the VTAM CINIT PSERVIC indicates a model number instead of a screen size, the MFS device characteristics table is not searched. A model number indicates a certain screen size and MFS device type.

The MFS device characteristics table is not searched if the VTAM CINIT PSERVIC field contains a model number instead of a screen size.

Related reading: For more information on using the MFSDCT utility (DFSUTB00), see IMS Version 15.2 System Utilities.