Joined: 30 Nov 2013 Posts: 822 Location: The Universe
There are two major reasons why many installations choose to use multiple CICS regions.
Classic CICS uses what is called cooperative multi-tasking. In this environment all the tasks run in what amounts to a single computing engine, even if multiple computing engines are available. This limits performance.
With cooperative multi-tasking. a single misbehaving application can effectively stop other applications.