Link3270 server adapter processing

The Link3270 server adapter enables a service requester to conduct an interactive BMS request and reply dialog with 3270 application programs that are running in CICS by using the CICS Link3270 bridge mechanism.

When the Link3270 server adapter is invoked during request processing, it performs the following actions:

Target 3270 application programs can use multiple output maps contained in one or more map sets. The map set load modules provide the definition of multiple maps used by the target 3270 application transaction programs. Each map set load module must be defined and available to the router region for Link3270 server adapter processing. This means that any map set used in target 3270 application transaction programs must be in a load library in the DFHRPL DD statement or concatenation of the CICS region in which CICS Service Flow Runtime is installed. Each map set load module must also be defined in that CICS system definition (CSD) file.

As the Link3270 server adapter provides 3270 emulation at the terminal level, it begins saving a copy of the application data structure when a SEND MAP ERASE command is issued. Additional business data and field attributes, from subsequent SEND MAP commands without the ERASE option, are merged with the saved application data structure. It is the saved application data structure, with the accumulated data, that is used in Link3270 server adapter processing.

Having been presented with the application data structure, the Link3270 server adapter can move business data from the application data structure to any output data container as modelled in the flow. If additional business data is required the Link3270 server adapter must submit additional transactions to the Link3270 bridge mechanism. To do this, input data may need to be supplied for certain fields on the current application data structure. The Link3270 server adapter may obtain this data either from any of it's input data containers or from data collected from previously run target 3270 applications.

Transaction routing processing

Link3270 server adapters support both dynamic transaction routing and transaction routing. The target CICS application transactions can be defined as remote or can be dynamically routed to remote regions using the CICS dynamic transaction routing facility. The Link3270 server adapter uses the Link3270 bridge mechanism to run 3270 transactions by linking to the DFHL3270 program in the router region and passing a COMMAREA that identifies the transaction to run and the data used by the target CICS application.

Link3270 server adapter processing steps in a transaction routing scenario are as follows:

  1. Run terminate processing in current target CICS region (bridge facility allocated)
  2. Deallocate currently allocated bridge facility
  3. Allocate new bridge facility in the new indicated target CICS region
  4. Run initiate processing where (TRANSaction = remote CICS system name/CONNECTION name with REMOTEName = CMAI or TRANSaction = local CICS system name /CONNECTION name with PROGram = DFHMALIN) in new target CICS region.
  5. Run target CICS application transaction routed to this new target CICS region.
For further information regarding CICS function request shipping (transaction routing method), see the CICS Intercommunication Guide. For programming information about the dynamic transaction routing program, see the CICS Customization Guide.
Note: New parameters on the interface allow the dynamic transaction routing program to identify Link3270 bridge requests and obtain the names of the target transaction and the bridge facility token.

For further information about the Link3270 bridge mechanism and its support for these types of intercommunication methods, see the section on "Transaction Routing considerations" and the section on "Using Link3270 bridge load balancing" in the CICS External Interfaces Guide Version 2 Release 2.