A technology hidden to the common man

Despite the predominance of mainframes in the business world, these machines are largely invisible to the general public, the academic community, and indeed many experienced IT professionals. Instead, other forms of computing attrct more attention, at least in terms of visibility and public awareness. That this is so is perhaps not surprising. After all, who among us needs direct access to a mainframe? And, if we did, where would we find one to access? The truth, however, is that we are all mainframe users, whether we realize it or not (more on this later).

Most of us with some personal computer (PC) literacy and sufficient funds can purchase a notebook computer and quickly put it to good use by running software, browsing websites, and perhaps even writing papers for college professors to grade. With somewhat greater effort and technical prowess, we can delve more deeply into the various facilities of a typical Intel®-based workstation and learn its capabilities through direct, hands-on experience, with or without help from any of a multitude of readily available information sources in print or on the web.

Mainframes, however, tend to be hidden from the public eye. They do their jobs dependably (indeed, with almost total reliability) and are highly resistant to most forms of insidious abuse that afflict PCs, such as email-borne viruses and trojan horses. By performing stably, quietly, and with negligible downtime, mainframes are the example by which all other computers are judged. But at the same time, this lack of attention tends to allow them to fade into the background. Furthermore, in a typical customer installation, the mainframe shares space with many other hardware devices: external storage devices, hardware network routers, channel controllers, and automated tape library “robots,” to name a few. The mainframe is physically no larger than many of these devices and generally does not stand out from the crowd of peripheral devices. There are different classes of  ainframe to meet diverse needs of customers. The mainframe can grow in capacity as businesses grow. So, how can we explore the mainframe’s capabilities in the real world? How can we learn to interact with the mainframe, learn its capabilities, and understand its importance to the business world? Major corporations are eager to hire new mainframe professionals, but there is a catch: some previous experience would help. 

What is special about mainframes?

MVS(Multiple Virtual Storage) is the primary operating system on the IBM 370 series of Mainframes. (You may hear people use various initials and four-digit numbers when referring to IBM mainframes, such as 3033, 3090 or ES9000, but they are all considered hardware models of the 370 series.) MVS is the eighteen-wheeler of operating systems. People don't use it for flash and speed; they use it to bear large, heavy loads steadily and dependably.

When we talk about the tremendous processing power of a mainframe running MVS, we're talking about a power different from that of supercomputers. Supercomputers do complicated calculations at very high speeds. Designing them for the best possible calculation speed often means sacrificing I/O (input/output) speed; the scientists who use them are more likely to give them a complex math problem and say "grind away at this equation all night" than they are to say "read in these 300,000 records of data, do 8 calculations on each, and then output 300,000 separate reports." Reading and writing a tremendous amount of data and doing relatively simple calculations with it (for example, calculating interest payments, as opposed to calculating a boat hull's optimum shape) is the province of mainframes running MVS. An insurance company keeping track of its accounts, a chain of stores keeping track of its inventory, or any large company keeping track of its employees and payroll would use MVS. Because it's a multi-user operating system, MVS lets

many different users use the same programs and data at once.

Personal computer users like to make fun of big computers running MVS, calling them "dinosaurs." While the interface may seem primitive, MVS has had many features since its introduction in 1974 that people are only now trying to shoehorn into the operating systems that control personal computer networks. MVS includes built-in recovery routines for dealing with faulty hardware like tape drives or even (in a multi-processor environment) faulty processors. A system running MVS can support thousands of users at once. The security of one user's data against tampering by others is an integral part of the system, designed into it from the ground up. (How often do you hear of a virus or a worm breaking into an MVS system?) The primitive interface isn't the only thing that give people the wrong idea about MVS. A given MVS installation is highly customizable, and so is the way that each user uses it. Many different parameters can be set when doing virtually anything, and MVS doesn't always have the default settings that we take for granted on other systems. The most efficient settings are left to individual system administrators to figure out. Since many settings and details are site-specific, a new user on a particular system—no matter how much MVS experience he or she brings to that system can't be expected to know the best way to approach that system.