A business application should incorporate the key design elements of components, transactions, and error handling. This section provides some more background to show how CICS supports the application designer to structure an application so that it meets the business requirements described in Chapter 1, and incorporates the key design elements. CICS provides the following facilities:
An environment for executing presentation logic and business logic components
Calls between components
Efficient control of concurrently running application programs serving many online users
Provision of ACID properties through management of the units of work (see the following section)
Shared error handling
It’s useful at this point to look at CICS transactions, and CICS programs and linking, in more detail. We’ll also consider how CICS deals with critical activities such as error handling and security.
In a CICS application, a transaction is the processing initiated by a request, usually from an end user. A transaction starts, executes, and ends. A single business transaction (such as the enrollment of a new customer) may involve several CICS transactions.
As well as referring to a single event, transaction can also refer to the class of similar events. Thus, we speak of adding Mary Smith to the payroll file with a (single) add transaction, but we also speak of the add transaction, meaning the class of additions to that particular ...