1.1 What is a mainframe? Today, the term mainframe can be used to describe a style of operation, applications, and operating system facilities. Here is a working definition: "A mainframe is what businesses use to host their commercial databases, transaction servers, and applications that require a greater degree of security and availability than is commonly found on smaller-scale machines." A mainframe is the central data repository or hub in a corporation's data processing center, linked to users through less powerful devices such as workstations or terminals. The presence of a mainframe often implies a centralized form of computing, rather than a distributed form of computing. Having data centralized in a single mainframe repository saves users from having to manage updates to more than one copy of their business data. This increases the likelihood that the data is current and has integrity, because there is only one version of data. Early mainframe systems were housed in enormous, room-filling metal boxes or frames, and this is probably how the term "mainframe" originated. The mainframe required large amounts of electrical power and air-conditioning,