Sunday, 24 March 2019

Multitasking | CICS Multitasking | CICS Multithreading .

All of the operating systems that support CICS provide multitasking of their own, but CICS handles multitasking internally. This provides for a stable system that works the same way under any operating system

The basic features, and strengths, of CICS is its ability to multitask.
  • A task is the execution of an application program for a specific user. 
  • Multitasking means that CICS allows more than one task to be executed at the same time, which is essential in an environment where hundreds of users can be logged into CICS at the same time.
CICS - Multitasking and Multi threading.
  • Multithreading is a technique that allows all the users in a CICS region to use the same copy of a program at the same time. For example, one transaction may begin to execute an application program.
CICS - Multitasking and Multi threading.

For example, you can see that both User 1 and User 5 are running the order entry program. In this case, if both users had their own copies of the program, valuable internal storage space would be used unnecessarily. With multithreading, though, only one copy of a program is loaded and shared by all.

For multithreading to work, the program must be reentrant. A program that's completely reentrant doesn't change itself in any way. In other words, a truly reentrant program cannot modify data in working storage.

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