What is a mainframe?

Mainframe is a computer that supports dozens of applications and input/output devices to serve tens of thousands of users simultaneously.The general term "mainframe" refers to large computers like those in the IBM System z9 and eServer zSeries processor families.What separates the mainframe from other computers is not just its processing capabilities. A mainframe has redundant features and system health awareness capabilities that enable it to deliver 99.999% availability.Mainframes are used by large organizations as their central transaction processing system. Transaction processing in this context requires high availability, security, performance, and responsiveness.