Date: 10 Apr 2015

Mainframe computers are multi-user, multi-programming and high performance computers. They operate at a very high speed, have very large storage capacity and can handle and powerful systems generally used in centralized databases. Mainframe computers are called organizational computers as they are used in large organizations.

Mainframe computers occupy more space and requires lots of staff to operate and maintain. They offer centralized form of computing. According to IBM, “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.”

One system can run multiple operating systems. Some of the operating systems are s/OS, s/VM, z/VM, z/VSE and Linux. The widely used one is z/OS. It can thousands of programs and users concurrently. It divides the given job into portions and give them to many independent system components and subsystems.

A sysplex is a set of z/OS systems that uses software and hardware to provide near-continuous availability. The core part is coupling facility. It is a special operating system that holds mainframes together. It provides a shareable memory. Parallel sysplex is a clustering technology used by customers to operate many OS copies as single system. This is flexible enough to allow users to add or remove applications. Concurrent read/write access to shared data from servers is possible.

Advantages
1. Extensive problem-solving capabilities
2. Faster
3. High memory capacity
4. Ability to handle multiple applications
5. Ability to act as a database server
6. Ability to do complex problem solving and large-volume jobs

Disadvantages
1. Expensive
2. Need lot of space and dedicated environment management
3. Special operating system required