
88 Introduction to the New Mainframe: Large-Scale Commercial Computing
5.1 Introduction to availability
In simplest terms, availability means how much the computer system is
available to its users, and the ideal is 100% of the time. This chapter discusses
the availability needs of commercial data processing and the evolution of the
hardware and operating system to fulfill these needs.
The transition of businesses to an online 24/7 environment is briefly discussed
here, along with the forces that are driving this requirement: the World Wide
Web, a worldwide client base, and regulatory requirements. However, our
primary focus is on the inhibitors ...