Introduction to Database

Management System

The Traditional Approach To Data Management

– Create new files for each application

– Data redundancy

– Data integrity

Disadvantages of File Processing

• Program-Data Dependence

– All programs maintain metadata for each file they use

• Data Redundancy (Duplication of data)

– Different systems/programs have separate copies of the same data

• Limited Data Sharing

– No centralized control of data

• Lengthy Development Times

– Programmers must design their own file formats

• Excessive Program Maintenance

– 80% of of information systems budget

Components of the database environment

Components of theDatabase Environment

• CASE Tools – computer-aided software engineering

• Repository – centralized storehouse of metadata

• Database Management System (DBMS) – software for managing the database

• Database – storehouse of the data

• Application Programs – software using the data

• User Interface – text and graphical displays to users

• Data Administrators – personnel responsible for maintaining the database

• System Developers – personnel responsible for designing databases and software

• End Users – people who use the applications and databases

Disadvantages of DBMS

• Databases used in enterprises may involve additional

risks as compared to a conventional data processing

system in some areas

• Confidential, Privacy and Security : When

information is centralized and is made available to

users from remote locations, there is a possibility of

unauthorized users accessing sensitive information.

• It is necessary to take technical, administrative and

legal measures.

Disadvantages of DBMS

• Data Quality : Since database is accessible to users remotely, adequate controls are needed to control users updating data and to control data quality.

• With increased number of users accessing directly,there is an opportunity for users to damage data.Unlessthere are suitable controls, the data quality may becompromised.

• Data Integrity : Since a large number of users cloud be using a database concurrently, technical safeguards are necessary to ensure that data remain correct during operation.

Overall System Structure

Overall System Structure

• A database system is partitioned into

modules which handles different

responsibilities of over all system.

The functional components of a database

system are

Query processor Component

Storage manager component

Query Processor Component

• DML Compiler : It translates DML statements

into a lower level instructions that the query

evaluation engine understands

• Embedded DML precompiler : It converts DML

statements embedded in an application program

into normal procedure calls in the host language.

• DDL Interpreter : It interprets DDL statements

and records them in a set of tables

• Query evaluation engine : It executes lower level

instructions generated by the DML compiler

Storage manager component

• It is an Interface between the data stored in the database and the application programs and queries submitted to the system.

• Authorization and Integrity manager : It tests for satisfaction of integrity constraints and checks the authority of users to access data.

• Transaction Manager : It ensures concurrent transactionexecutions processed without conflicting.

• File manager : It manages the allocation of space on diskand the data structures used to represent information.

• Buffer manager : Which is responsible for fetching datafrom disk storage into main memory.

Application Architectures

Two-tier architecture: E.g. client programs using ODBC/JDBC to

communicate with a database

Three-tier architecture: E.g. web-based applications, and

applications built using “middleware”