March 2013 Archive


The Worlds of Database Systems

Databases today are necessary to each business. They are used to maintain internal records, to present data to customers and clients on the World-Wide-Web, and to support many other commercial processes.

The Evolution of Database Systems

What is a database? In real meaning a database is nothing more than gathering of information that exists over a long phase of time, often many years.

Early Database Management Systems

The first commercial database management systems appeared in the late 1960's. These systems evolved from file systems, which offer some of item (3) above; file systems accumulate data over a long phase of time, and they allow the storage of huge amounts of data.

Airline Reservations Systems

In this kind of system, the items of data include: 1. Reservations by a single customer on a single flight, including such information as assigned seat or meal preference.

Banking Systems

The Data items contain names and addresses of customers, accounts, loans, and their balances, and the connection between customers and their accounts and loans, e.g., who has signature authority over which accounts.

Corporate Records

Many early applications concerned corporate records, such as a record of each sale, information about accounts payable and receivable, or information about employees their names, addresses, salary, benefit options, tax status, and so on.

Relational Database Systems

Following a famous paper written by Ted Codd in 1970, database systems changed considerably. Codd suggested that database systems should present the user with a view of data arranged as tables called relations.

Smaller and Smaller Systems

In the beginning, DBMS's were large, expensive software systems running on large computers. The size was compulsory, because to store a gigabyte of data required a large computer system.

Bigger and Bigger Systems

On the other hand, a gigabyte isn't much data. Commercial databases often consume hundreds of gigabytes. Moreover, as storage becomes cheaper people find new reasons to store greater amounts of data.

Tertiary Storage

The biggest databases today need more than disks. Several kinds of tertiary storage devices have been developed. Tertiary devices, perhaps storing a terabyte each, need much more

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