3270 and SLU 2 input substitution character

A X'3F' can be received on input by IMS TM from some terminals (such as by using the ERROR key).

The substitution character (X'3F') provides a means of informing the host application that an error exists in the field. MFS also uses X'3F' for IMS TM functions on input data streams. To eliminate the confusion resulting from the two uses of the X'3F' characters, a parameter (SUB=) is provided on the DEV statement for use with 3270 and SLU 2 display devices.

With this parameter, a user-specified character can be defined to replace any X'3F' characters received by MFS in the 3270 and SLU 2 data stream. No translation occurs if any of the following is true:

• The SUB= parameter is not specified.
• The SUB= parameter is specified as X'3F'.
• The input received bypasses MFS.

The specified SUB character should not appear elsewhere in the data stream, so, it should be nongraphic.