Introduction to Database Introduction to Database Management SystemManagement System

The Traditional Approach To Data The Traditional Approach To Data ManagementManagement

– Create new files for each application

– Data redundancy

– Data integrity

Disadvantages of File ProcessingDisadvantages 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 theComponents of theDatabase EnvironmentDatabase 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 DBMSDisadvantages 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 DBMSDisadvantages 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.Unless there are suitable controls, the data quality may be compromised.

• 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

Overall System StructureOverall 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 ComponentStorage manager component

Query Processor ComponentQuery 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 componentStorage 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 transaction executions processed without conflicting.

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

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

Application ArchitecturesApplication Architectures

Two-tier architecture: E.g. client programs using ODBC/JDBC to communicate with a databaseThree-tier architecture: E.g. web-based applications, and applications built using “middleware”