INTRODUCTION OF DATABASE SYSTEMS :
A database management system (DBMS) is a collection of programs that manages the database structure and controls access to the data stored in the database. In a sense, a database resembles a very well-organized electronic filing cabinet in which powerful software, known as a database management system, helps manage the cabinet’s contents.
The metadata provide a description of the data characteristics and the set of relationships that links the data found within the database. For example, the metadata component stores information such as the name of each data element, the type of values (numeric, dates, or text) stored on each data element, whether or not the data element can be left empty, and so on. The metadata provide information that complements and expands the value and use of the data. In short, metadata present a more complete picture of the data in the database. Given the characteristics of metadata, you might hear a database described as a “collection of self-describing data.”DATABASE SYSTEMS
Imagine trying to operate a business without knowing who your customers are, what products you are selling, who is working for you, who owes you money, and whom you owe money. All businesses have to keep this type of data and much more; and just as importantly, they must have those data available to decision makers when they need them. It can be argued that the ultimate purpose of all business information systems is to help businesses use information as an organizational resource. At the heart of all of these systems are the collection, storage, aggregation, manipulation, dissemination, and management of data.DATABASE SYSTEMS
Depending on the type of information system and the characteristics of the business, these data could vary from a few megabytes on just one or two topics to terabytes covering hundreds of topics within the business’s internal and external environment. Telecommunications companies such as Sprint and AT&T are known to have systems that keep data on trillions of phone calls, with new data being added to the system at speeds up to 70,000 calls per second!1 DATABASE SYSTEMS
Not only do these companies have to store and manage these immense collections of data, they have to be able to find any given fact in that data quickly. Consider the case of Internet search staple Google. While Google is reluctant to disclose many details about its data storage specifications, it is estimated that the company responds to over 91 million searches per day across a collection of data that is several terabytes in size. Impressively, the results of these searches are available nearly instantly.DATABASE SYSTEMS