Coding considerations for sequential terminals

For example, the first record usually starts with a transaction code, to tell CICS what transaction to execute. The transaction code must start in the first position of the input, just as it must on a real terminal. Note that this limits the ability to test applications that require input in complex formats. For example, there is no provision for expressing a formatted 3270 input stream as a sequential file, because of all the complex control sequences. However, you can use an unformatted 3270 data stream (or any other similar stream) for input, and you can still use BMS to format your output.

When you build the input file, you place an end-of-data indicator (EODI) character after each of your input records. The EODI character is defined in the system initialization table; the default value is a backslash ('\', X'E0'), but your installation may have defined some other value.

When processing the input stream, CICS observes EODI characters only. CICS does not analyze the record structure of the input file or device, which means that each input can span records in the input file. However, you must start each input on a new physical record to ensure each input is correctly processed.

The length of an input record (the number of characters between EODIs) should not exceed the size of the input buffer (the INAREAL value in the LINE component of the sequential terminal definition). If it does, the transaction that attempts to RECEIVE the long record abends, and CICS positions the input file after the next EODI before resuming input processing.

An end-of-file marker in the input also acts as an EODI indicator. Any RECEIVE command issued after end-of-file is detected also causes an abend.