Overview of Database

Database is a collection of related data organised in a way that data can be easily accessed, managed and updated. Any piece of information can be a data, for example name of your school. Database is actualy a place where related piece of information is stored and various operations can be performed on it.


DBMS is a software that allows creation, definition and manipulation of database. Dbms is actualy a tool used to perform any kind of operation on data in database. Dbms also provides protection and security to database. It maintains data consistency in case of multiple users. Here are some examples of popular dbms, MySql, Oracle, Sybase, Microsoft Access and IBM DB2 etc.

Components of Database System

The database system can be divided into four components.

  • Users : Users may be of various type such as DB administrator, System developer and End users.
  • Database application : Database application may be Personal, Departmental, Enterprise and Internal
  • DBMS : Software that allow users to define, create and manages database access, Ex: MySql, Oracle etc.
  • Database : Collection of logical data.

Functions of DBMS

  • Provides data Independence
  • Concurrency Control
  • Provides Recovery services
  • Provides Utility services
  • Provides a clear and logical view of the process that manipulates data.

Advantages of DBMS

  • Segregation of applicaion program.
  • Minimal data duplicacy.
  • Easy retrieval of data.
  • Reduced development time and maintainance need.

Disadvantages of DBMS

  • Complexity
  • Costly
  • Large in size

Database Architecture

Database architecture is logically divided into two types.
  1. Logical two-tier Client / Server architecture
  2. Logical three-tier Client / Server architecture

Two-tier Client / Server Architecture

Two-tier Client / Server architecture is used for User Interface program and Application Programs that runs on client side. An interface called ODBC(Open Database Connectivity) provides an API that allow client side program to call the dbms. Most DBMS vendors provide ODBC drivers. A client program may connect to several DBMS's. In this architecture some variation of client is also possible for example in some DBMS's more functionality is transferred to the client including data dictionary, optimization etc. Such clients are called Data server.

Three-tier Client / Server Architecture

Three-tier Client / Server database architecture is commonly used architecture for web applications. Intermediate layer called Application server or Web Server stores the web connectivty software and the business logic(constraints) part of application used to access the right amount of data from the database server. This layer acts like medium for sending partially processed data between the database server and the client.