What is Mainframe?
Mainframe is a powerful, high-end computer which supports several hundreds or thousands of users simultaneously. Thereby its usage is widely spread among the large businesses that involves high-volume, high-performance and processor-intensive tasks. Its also an expensive computer capable of organizing and executing multiple processing tasks at awe-inspiring speeds.
Why Mainframe is so powerful?
- Security: Mainframe provides multi-levels of security from boot password(Finds a disk where Operating System resides and asks for a password) to table-level security.
- Multi-threading: Mainframe is capable of dividing a program into multiple threads(parts) and executing them parallel at the same time communicating internally with each thread via shared memory. Because of this concurrent/multi-threading facility, it can free a resource when not in use. This results in less memory usage and higher performance gain.
- Multiprocessing: Having more than one processor(CPU) within the same OS. If one processor goes offline, other can take over, which avoids risks of losing information. By this way processor load can be shared among different processors present, hence increasing the lifetime of each processor.
- Spooling: Commonly referred to Print Spooling, which allows user to place all the print jobs in a buffer(temporary memory), so that user is free to perform other tasks while the printer can engage itself in finishing the jobs at its own rate whenever it is ready.
- Multi-programming: Execution of different programs concurrently by CPU which makes use of the CPU's idle time. By this way, CPU need not wait until a particular task completes, instead it makes use of this wait period to perform other tasks.
How Mainframe Functions?
The power of mainframe lies in the fact that it uses different layers to perform its various activities. Below are its layers:
- MVS(Multi Virtual System): Mainframe's Operating System.
- TSO(Time Sharing Optimizer) & ISPF(Inter-system Productivity Facility: Takes care of multitasking and multi-programming.
- JCL(Job Control Language): It acts as mediator between MVS and programs written in COBOL, Assembler or PL/I. Without JCL a program will not run on a Mainframe Computer.
- CICS(Customer Information Controlling System): Its an interface between Application programs and Mainframe's operating system.
- VSAM(Virtual Storage Access Method): Different modes by which data storage and retrieval could be done efficiently.
- DB2: Its a Relational Database Management System(RDBMS) which allows users to build, access and maintain databases using SQL.