Friday 27 February 2015

What are mainframe computers?

IBM Mainframes

What are mainframe computers?

mainframe computer is a big computer. IBM builds mainframe computers. Today, a mainframe refers to IBM's System Z servers. Many large corporations like banks, insurance companies, travel and retail sector, telecom companies process data on a mainframe. Today, thousands of people around the globe book flights, do wire transfers, make credit-card purchases. These transactions are processed in a snap by a mainframe.

Mainframe RAS features:

Reliability is the ability of computer hardware or software to consistently perform according to its specifications. Mathematically, reliability measure is the mean time to failure(MTTF). Availability is the ratio of the up time of a system to the total time. Serviceability is an expression of the ease with which a system can be maintained or repaired.

The reliabilityavailability and serviceability features are in the System Z's DNA. System Z is designed to provide an availability of 99.999% (five 9s). The "Z" in System Z's brand-name stands for zero down-time. System Z servers have reported an MTTF of 40 years. Organizations run their mission-critical applications on mainframe to provide 24/7 availability.

System Z processors use an instruction retry mechanism. Every instruction that executes successfully on the System Z processor is check pointed, the processor state is saved. If an error is detected, a recovery sequence commences. The processor is fenced off. The processor state is refreshed from the last checkpoint and the instruction is retried. Like having spare tires on a truck, System Z offers chip redundancy. If one processor fails, System Z can dynamically switch to a spare without losing a beat! Thousands of error checkers(parity, residue, illegal state, hardware redundancy compares and so on) are embedded on the chip.

Are Mainframe computers good at everything?

Well, not quite. Mainframes are not good at number-crunching or don't do scientific calculations. A Mainframe is not a Super-computer. You would n’t use a Mainframe computer to calculate the value of Pi, up to 1000-decimal Places. Mainframe-Computers are not meant for speed. They are n’t fast, rather they can process humungous data reliably. You can't play games like Counter-Strike or Half-Life on a Mainframe. 

Mainframe computers don’t have a beautiful user-interface like the PC at your home. You would n’t find a desktop wallpaper or icons on a mainframe computer.
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Below are the Tutorials to learn IBM Mainframes Technologies.

JCL Tutorial  

COBOL Tutorial

VSAM Tutorial

DB2 Tutorial

CICS Tutorial

IMS DB Tutorial






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