Chapter 15. Intercommunication considerations
This chapter provides only a summary of what you need to consider when you write applications that communicate with other CICS systems. For further information, see the
CICS Family: Interproduct Communication
book and the
CICS for iSeries Intercommunication
book.
You can run application programs in a CICS intercommunication environment using one or more of the following: v
Transaction routing
—enables a terminal in one CICS system to run a transaction in another CICS system. v
Function shipping
—enables your application program to access resources in another CICS system. v
Distributed program link (DPL)
—enables an application program running in one CICS system to link to another application program running in a remote
CICS system. v
Asynchronous processing
—enables a CICS transaction to start another transaction in a remote system and optionally pass data to it. v
Distributed transaction processing (DTP)
—enables a CICS transaction to communicate with a transaction running in another system.
There is one interface available for DTP: command-level EXEC CICS. The
Systems Application Architecture
*
(SAA) interface for DTP called CPI
Communications (Common Programming Interface Communications) is not directly supported by CICS/400.
Design considerations
If your application program uses more than one of these facilities, you obviously need to bear in mind the design considerations for each one. Also, if your program uses more than one intersystem session for distributed transaction processing, it must control each session according to the rules for that type of session.
Transaction routing
Transactions that can be invoked from a terminal owned by another CICS system, or that can acquire a terminal owned by another CICS system during transaction initiation, must be able to run in a transaction routing environment.
Generally, you can design and code such a transaction just like one used in a local environment. However, there are a few restrictions related to basic mapping support (BMS), pseudoconversational transactions, and the terminal on which your transaction is to run. All programs, tables, and maps that are used by a transaction
must
reside on the system that owns the transaction. (You can duplicate them in as many systems as you need.)
Some CICS transactions are related to one another, for example, through common access to the CWA or through shared storage acquired using an EXEC CICS
GETMAIN command. When this is true, the system programmer must ensure that these transactions are routed to the same CICS system.
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