Monday, April 02, 2007

Review topic: CICS: pseudo-conversational programming


One of the most important interview concepts in CICS programming is pseudo-conversational applications program.

A program will end (stop executing and using memory) after the end user does a SEND. Later, when the user presses and attention identifier (AID key – such as Enter, a PF key, a PA key, or Clear, CICS will restart the program, most often with a RECEIVE of a map filled in with data.

In conversational programming, the program would not end, and with many users, an installation could go SOS or “short on storage.”

The execution of a specific program (as restarted by pressing the key) is called a task. Restarting a program starts a new “task.” A program is associated with a transaction (trans-id) in an internal table called the PCT, or program control table. The Procressin Program Table, or PPT, monitors each program and whether it is loaded into storage.

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