For performance measurements we need to be very specific about what we are measuring. Therefore, it is necessary to define a few terms.
The word user here means the terminal operator. A user, so defined, sees CICS® performance as the response time, that is, the time between the last input action (for example, a keystroke) and the expected response (for example, a message on the screen). Several such responses might be required to complete a user function, and the amount of work that a user perceives as a function can vary enormously. So, the number of functions per period of time is not a good measure of performance, unless, of course, there exists an agreed set of benchmark functions.
A more specific unit of measure is therefore needed. The words transaction and task are used to describe units of work within CICS. Even these can lead to ambiguities, because it would be possible to define transactions and tasks of varying size. However, within a particular system, a series of transactions can be well defined and understood so that it becomes possible to talk about relative performance in terms of transactions per second (or minute, or hour).
In this context there are three modes of CICS operation.
Nonconversational mode is of the nature of one question, one answer; resources are allocated, used, and released immediately on completion of the task. In this mode the words transaction and task are more or less synonymous.
Conversational mode is potentially wasteful in a system that does not have abundant resources. There are further questions and answers during which resources are not released. Resources are, therefore, tied up unnecessarily waiting for users to respond, and performance may suffer accordingly. Transaction and task are, once again, more or less synonymous.
Pseudoconversational mode allows for slow response from the user. Transactions are broken up into more than one task, yet the user need not know this. The resources in demand are released at the end of each task, giving a potential for improved performance.
The input/output surrounding a task may be known as the dialog.