Designing applications for recovery

In this context, application refers to a set of one or more transactions designed to fulfill the particular needs of the user organization. A transaction refers to a set of actions within an application which the designer chooses to regard as an entity. It corresponds to a unit of execution, which is typically started in a CICS® region by invoking the transaction by its identifier from a terminal attached to CICS.

As an application designer, you must decide how (if at all) to subdivide an application into transactions, and whether the transactions should consist of just one unit of work, or more than one.

Ideally, but not necessarily, a transaction would correspond to a unit of work. Dividing the business application into units of work that correspond to transactions simplifies the entire recovery process.

An example of a typical business application is an order-entry system. A typical order-entry application includes all the processes needed to handle one order from a customer, designed as a set of processing units, as follows:

1. Check the customer’s name and address and allocate an order number.
2. Record the details of ordered items and update inventory files.
3. Print the invoice and shipping documents.

Depending on the agreed recovery requirements statement, you could design noting details of ordered items and updating files either as one large transaction or as several transactions, with one transaction for each item within the order.