HTML templates generated from BMS maps

The 3270 display system and HTML forms have a number of similarities. BMS map templates can represent the features of the 3270 display.

Attention: This topic contains Product-sensitive Programming Interface and Associated Guidance Information.
The features of the 3270 display system have many parallels with HTML forms:
  • In both cases, the display area can contain fixed text and areas where the user can enter data.
  • The AID keys on the 3270 keyboard have a similar function to the buttons displayed on an HTML form.
  • In both cases, you can detect whether the user has modified the contents of a data entry field.
Templates generated from BMS maps contain a number of elements to represent the features of the 3270 display:
  • Protected fields in the map are displayed as typical HTML text.
  • Unprotected fields in the map are displayed as text input elements. CICS® gives each element a 2-part name, which can be up to 32 characters long:
    • The first part of the name is 11 characters long, and has the following form: 
      Frrcccllll_
      where
      • rr is a 2-digit number that denotes the row in which the field is displayed on a 3270 screen.
      • ccc is a 3-digit number that denotes the column in which the field is displayed on a 3270 screen.
      • llll is a 4-digit number that denotes the length of the field.
    • For BMS fields that are named in the map, the second part consists of the name used in the map, truncated if necessary to 21 characters.
    • For BMS fields that are unnamed, the second part is of the form DFH_nnnn where nnnn is a 4–digit number. The fields are numbered sequentially as they are encountered in the BMS map.
    For example, suppose that the third unnamed and unprotected field is located at row 2 and column 11 of the screen, and has a length of 16 characters. The generated 2-part name is: 
    F020110016_DFH0003
    Now suppose that the same field has a name of TOTAL_MONTHLY_PURCHASES in the BMS map. The name that CICS generates for the HTML element is: 
    F020110016_TOTAL_MONTHLY_PURCHAS
    Note: The sequence in which fields are displayed on the 3270 screen might not be the same as the sequence in which they are coded in a BMS map definition. When the corresponding template is displayed on a web client, the fields are displayed in the sequence in which they are coded.
  • Each attention key supported by the 3270 display is simulated as a submit button. The buttons are named:
    • DFH_PF01 through DFH_PF24
    • DFH_PA1 through DFH_PA3
    • DFH_ENTER, DFH_CLEAR
    When the user selects one of these buttons, the corresponding variable is transmitted in the HTTP request. CICS uses the variable to determine which AID to simulate in the 3270 application.

    An additional submit button named DFH_PEN is used with detectable fields.

  • Detectable fields are simulated as text elements with a preceding check box. Refer to Using detectable fields.
  • A hidden element (DFH_STATE_TOKEN) is used to maintain the display state seen by the application over a number of interactions with the web client.
  • A hidden element (DFH_CURSOR) and a JavaScript function (dfhinqcursor()) cooperate to return the cursor position to the application.
  • A series of hidden elements (DFH_NEXTTRANSID.1 to DFH_NEXTTRANSID.n) are used to capture a transaction ID entered in a web client field.