What is Task and Transaction in Mainframe Systems

Task - The tast is a unique, basic unit of work scheduled by the OS or CICS. A task can,
* Read from and write to the terminal.
* Read and write files.
* start another task.

Transaction

A transaction is an entity which initiates execution of a task. In CICS, every transaction is identified by a 4 character transaction identifiers (TRANSID). The transaction IDs are placed in the DCT by the system programmer.

CICS Features - Multitasking

As dicussed earlier a task is the execution of an application program for a specific user. Multitaking refers to running multiple tasks at the same time. within CICS, tow or more.

Multithreading

Multithreading allows two or more users can access the same copy of a program at the same time. CICS accomplihes this by providing a seperate copy of working storage for each user running the program.