Support of DPL (Distributed Program Link) programs

CICS provides different programming interfaces to invoke another CICS program or to allow a program to be invoked by another CICS program. Two of these facilities are important here.

• DTP (Distributed Transaction Processing) which enables a CICS transaction to communicate with a CICS application running in another system by exchanging messages. DTP programs are coded using the APPC programming interface.

• DPL (Distributed Program Link) which enables a CICS program to invoke a program in another CICS system and wait for the called program to return. Data is exchanged between the programs in a communication area (COMMAREA). DPL is similar to a remote procedure call.

BeanConnect makes it possible to invoke outbound transactions via DTP. However, it is not possible to call a DPL program directly. For this, a DTP program is needed in which the program link is wrapped.

A DPL program is called with the CICS LINK command, which has three important parameters:

• PROGRAM to specify the name of the program to which control is to be passed unconditionally

• COMMAREA to specify the communication area that is made available to the linked program

• LENGTH which specifies the length in bytes of the communication area.

The input data for the distributed program call is received in a message. The input data must be copied to the communication area. The required output data has to be sent as response to the EJB when the linked program returns.