Introduction

Database integral part of our day to day life Collection of related database Database Management System : software

managing and controlling access to the database.

Database system : collection of application interracting with database

Example of use of database systemsA database is accessed when :

Purshasing in a supermarket ( item price) Purchase using credit cards ( valid cards) Inquiries about a holliday (flight details) Make a loan (library) Rent video ( detail info on each video) Online bookstore( book details)

Sample data

Dtabase in the dev cycleProject

Identifcation and Selection

ProjectInitiation

and Planning

Analysis

Logical Design

PhysicalDesign

Implementation

Maintenance

Database A repository of data simultaneously used by many

users (a shared ressource). Collection of logically related data. Description of this data (data dictionary) BDMS

Software interracting with : Users Application programs database

BDMSSoftware interracting with : Users Application programs Database

DBMS allows users (using a query language): Insert Update Delete Retrive data from DB

Database application programsComputer program that allow users to interact with the DB through DBMS.

DBMS environment Hardware :Computer systems that DBMS and

application programs run on. Software: DBMS,application programs, operating

system, network software(if DBMS used over network).

Data ( operational data and meta-data) Procedures: instruction and rules that govern use of

database People: DB designer, administrators , programmers

and end users

Database environment

DBMS architecture2 layer architecture Client-Server The client that runs the application and the server that

handles the database back-end Multiple users able to access the DB simultanousely. Server is processing data while the client for business

logic and presentation.

2-Tier Architecture

DBMS architecture

3 layer architecture User Interface layer ( runs on the user´s client) Business logic (middle layer) and data processing

layer. Runs on a server called ”application server”. DBMS ( store data ) , may run on a separate server

called ”database server”

3 layer architecture advantages Thin client (less hardware) , client only handling

presentation logic.This means a little communication needed between the client(browser) and the middle tier.

Separating the core business logic from the database functions

Modularity : Easy to modify or replace one tier without affecting the other tiers

Easier load balancing Maps quite naturally to the web environment Security : middle tier protecting the DB. Scalabale : add as many middle tier as needed

Functions of a DBMS

Data storage , retrieval and update

A user-accessible Catalog

Hold data about the structure of database , users , applications and so on

Transaction support

Ensure that all the updates are made or that none of them are made

Concurrency control services

Enable many users to access shared data concurrently

Recovery services

When transaction fails, DB revovered to a consistent state

Functions of a DBMS

Autorization services

Only special part could have access to info

Support for data communication

Terminal at remote locations can communicate with host of DBMS through network

Integrity Services

Stored data are consistent and correct

Services to promote Data Independence

Utility Services

Utility program help manage the DB effectively

Advantages of DBMS Control of data redundancy (duplication)

Eliminate redundency where possible ,

Data consistency Data stored in more than once , system can ensure that all copies

of the data are kept consistent

Sharing of data By all authorized users

Improved data integrity Rules that DB is not permitted to violate User define data and DBMS enforce it

Improved maintenance through data independence Make application immune to changes in data description