Database introduction

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 systems
A 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)

Dtabase in the dev cycle
Project
Identifcation
and Selection
Project
Initiation
and Planning
Analysis
Logical
Design
Physical
Design
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

 BDMS
Software interracting with :
 Users
 Application programs
 Database
DBMS allows users (using a query language):
 Insert
 Update
 Delete
 Retrive data from DB

Database application programs
Computer 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

DBMS architecture
2 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.

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

Database introduction

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Database introduction