2.4. From real to virtual

“Virtual” is a word used by other manufacturers today. Virtual on one machine is not the same as on other machines. On the mainframe it is not only the memory that can be virtualized. On the mainframe, virtualization has been part of the design for over 30 years. It is the key factor that allows you to do consolidation on the mainframe. For more details on virtualization, see Chapter 7, “The Value of Virtualization.”

2.4.1. The roots of z/VM

In the 1960s, hardware was expensive, and it was imperative to use a computer as economically as possible, that is, to run it as much of the time as possible. The machine was needed to run existing business applications, and also to test new programs. Ideally, each tester needed ...

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