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 it is possible to detect whether the end 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 normal HTML text.
- Unprotected fields in the map are displayed as text input elements. CICS® gives
each element a two-part name, which can be up to 32 characters in length:
- The first part of the name is 11 characters long, and has the following
form:
Frrcccllll_
where - rr is a two-digit number which denotes the row
in which the field is displayed on a 3270 screen.
- ccc is a three-digit number which denotes the
column in which the field is displayed on a 3270 screen.
- llll is a four-digit number which 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 a length of 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 two part name is F020110016_DFH0003
Now
suppose the same field had a name of TOTAL_MONTHLY_PURCHASES in
the BMS map. The name which CICS generates for the HTML element is: F020110016_TOTAL_MONTHLY_PURCHAS
Note: The
sequence in which fields are displayed on the 3270 screen may 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 end 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. See Using detectable fields for more information.
- 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 through DFH_NEXTTRANSID.n)
are used to capture a transaction id entered in a Web client field.