Mainframe computers (colloquially
referred to as "big iron") are computers used primarily by
large organizations for critical applications, bulk data processing such
as census, industry and consumer statistics, enterprise resource
planning, and transaction processing.
The term originally referred to the large cabinets called "main
frames" that housed the central processing unit and main memory of
early computers. Later, the term was used to distinguish high-end
commercial machines from less powerful units. Most large-scale computer
system architectures were established in the 1960s, but continue to evolve.
Advantages of
mainframe systems
- High security: Used in Financial domain, Banks, leasing industries, Retail, Hospitals, ..
- Bulk amount of storage: data storage can be huge
- Multiple logins simultaneously: More than 25000 users can use this at a point of time.
- Scalable: memory expandable
Different
components of Mainframe systems
- Z/OS (Z/OS
is a 64-bit mainframe operating
system (OS) developed by IBM for
its family of z/Architecture enterprise mainframe computers,
including the zEnterprise 196 and zEnterprise 114) or MVS (Multiple
Virtual Storage)
- TSO (Time Sharing Option) - A tool in Z/OS tool that provides a single-user logon capability and a basic command prompt interface to z/OS
- ISPF (Interactive System Productivity Facility) - A tool in Z/OS or a full panel application navigated by keyboard. It includes a text editor and browser, and functions for locating and listing files and performing other utility functions
- COBOL (Common
Business Oriented Language) - High level language for mainframe
- JCL (Job
Control Language) - Low
level language for mainframe
- DB2 (DataBase
2) - Database
for Mainframe
- CICS (Customer
Information Control System) - Front end designing for mainframe
- REXX (Restructured Extended Executor) - Coding for automation in mainframe
Mainframe work load divided into 2 as below
- Batch processing – No user interaction needed. Tasks are scheduled and will be executed by automation. Time oriented process.
- Online transaction processing (OLTP) – system with user interaction.
Mainframe subsystem à
tasks in mainframe is given to different subsystems so that each will perform
specific tasks. Eg: TSO, IMS, DB2, JES, CICS
Files in z/os -> Physical Sequential Datasets (PS) à this is like a normal
file in windows
Folders in z/os à
Partitioned Dataset (PDS) à
this is like a folder in windows