DFHML1 (LU1 printer with extended attributes mapping)

The LU1 printer with extended attributes mapping program, DFHML1, is called in response to requests for BMS services involving terminals of the 3270 Information Display System. Figure 1 shows how the DFHML1 program responds to these requests.
Figure 1. LU1 printer with extended attributes mapping program interfaces
Diagram showing how the DFHML1 program responds to requests for BMS services involving 3270 terminals
Note:
  1. The following types of requests, by application programs communicating with LU1 printer mapping, pass information through the mapping control program (DFHMCP), and the page and text build program (DFHPBP), to DFHML1:
    • SEND MAP ACCUM
    • SEND MAP SET
    • SEND TEXT
    • SEND TEXT ACCUM
    • SEND TEXT SET

    For one page of output, DFHML1 acquires an area and formats it into a chain of control blocks known as map control areas (MCAs). Each MCA corresponds to one map on the page and contains information about chaining down the maps and processing the fields in each map. DFHML1 then builds the data stream directly from the maps and the TIOAs.

  2. Maps are either passed by the application program or loaded by DFHMCP.
  3. The address of a terminal input/output area (TIOA) is supplied by the application program for all requests.
  4. DFHML1 communicates with storage control to obtain and release storage for MCAs and for the mapped data.
  5. All requests (see note 1) are sent to a designated destination by the terminal page processor (DFHTPP), after the return of control to DFHPBP.