CICS web support and 3270 display applications

When a 3270 transaction is accessed by a web client, CICS® can display the output as an HTML form. Use the variants of the Web Terminal Translation Application (DFHWBTTA, DFHWBTTB, or DFHWBTTC) to provide web clients with access to applications that were originally designed to use the 3270 display system. CICS web support for 3270 applications supports the SEND, CONVERSE, and RECEIVE terminal control commands.

You can create an HTML form from the output of a 3270 transaction in one of two ways:
  • For applications that use BMS, an HTML template is generated from a BMS map and stored in the template library. You can customize the generation of the template. However, if the only changes you need to make to the generated HTML can be accommodated in the heading or footing section, you do not need to generate a template from the BMS map, because the map can be processed at execution time to generate the HTML form.
  • For applications that do not use BMS, the outbound 3270 data stream is processed at execution time to generate the HTML form.
You can be use the Web Terminal Translation Application to display the HTML forms to a web browser.
Note: The Web Terminal Translation Application operates at HTTP/1.0 level. It does not make full use of the facilities available in CICS web support, such as the EXEC CICS WEB API, and so does not comply with the HTTP/1.1 specification:
  • Requests from the web client and responses from the application are not checked against the HTTP protocol specification.
  • CICS does not provide HTTP/1.1 responses, in normal or error situations, even if the client is at HTTP/1.1 level.
All three variants of the Web Terminal Translation Application support nonconversational, conversational, and pseudoconversational transactions.
  • DFHWBTTA and DFHWBTTB perform the translation between 3270 data streams and HTML and between templates generated from BMS maps and HTML. Use DFHWBTTA if your HTML templates are 32,767 bytes (32 KB) of data or smaller, and use DFHWBTTB if your HTML templates are larger than 32 KB. (Using DFHWBTTB for smaller HTML templates incurs an unnecessary performance degradation.)
  • DFHWBTTC performs the translation between BMS maps and HTML when no template is generated. BMS maps used in this way must specify TERM=3270 or omit the TERM parameter. DFHWBTTC supports HTML output of any length. Use DFHWBTTC if you do not need to generate HTML templates.

DFHWBTTB and DFHWBTTC are aliases for DFHWBTTA; DFHWBTTA is called in each case. CICS uses the name by which the program is called to determine which processing is needed.

DFHWBTTA, DFHWBTTB, and DFHWBTTC generate HTML that conforms to the HTML 3.2 specification. If you use a web browser that does not support HTML 3.2, some functions might not work correctly.

HTML generated for terminals having a page size that results in a field position greater than 4095 (x'FFF') might not function correctly, particularly when using DFHWBTTC.

You can create URIMAP definitions that specify DFHWBTTA, DFHWBTTB, or DFHWBTTC as the program to be called to process a request (PROGRAM attribute). The method that the web client uses to access the program is similar, but the use of URIMAP definitions gives you an online administration facility that can be used to prevent or redirect requests. When a URIMAP definition is used, the use of an analyzer program is optional. Refer to URL path components for 3270 display applications.

CICS web support for 3270 applications supports the SEND, CONVERSE, and RECEIVE terminal control commands. It also supports minimum function BMS and the SEND TEXT command. The DEFRESP option on the SEND and CONVERSE commands is ignored. Application recovery might be affected.

CICS web support does not support partitions, logical devices codes, magnetic slot readers, outboard formatting, or other hardware features. You can use detectable fields with light pen support.