Multiprogramming and multiprocessing
Mainframe is capable of multiprogramming, or executing many programs concurrently, and of multiprocessing, which is the simultaneous operation of two or more processors that share the various hardware resources.
z/OS makes multiprogramming possible by capturing and saving all the relevant information about the interrupted program before allowing another program to execute. When the interrupted program is ready to begin executing again, it can resume execution just where it left off. Multiprogramming allows z/OS to run thousands of programs simultaneously for users who might be working on different projects at different physical locations around the world.
z/OS can also perform multiprocessing, which is the simultaneous operation of two or more processors that share the various hardware resources, such as memory and external disk storage devices.
The techniques of multiprogramming and multiprocessing make z/OS ideally suited for processing workloads that require many input/output (I/O) operations. Typical mainframe workloads include long-running applications that write updates to millions of records in a database, and online applications for thousands of interactive users at any given time.