Database Management Systems - جامعة نزوى · PDF fileDatabase Management Systems . 2...

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DATABASE CONCEPTS & APPLICATIONS

COMP 244

Database Management Systems

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What is a DBMS?

• A Database Management System (DBMS) is a software package designed to store and manage databases through database applications.

Database

Application(s) Database DBMS

User

User

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Examples of DBMS

• Personal – Files-based, dBase, Paradox, Access

• Multi-User/Client-Server/Web-Based – Oracle, DB2, Ingris, Sybase

• Personal Web-Based – MySQL

• Non-Relational – Object-Oriented Databases

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Advantages of a DBMS

• Data Independence – Applications insulated from how data is

structured and stored.

– Application programs should not be exposed to

details of data representation and storage

• The DBMS provides an abstract view of the

data

• Efficient Data Access – A DBMS utilizes sophisticated techniques to

store and retrieve data

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Advantages of a DBMS

• Data Integrity and Security – A DBMS can enforce integrity constraints

– A DBMS can enforce access controls that

govern what data is visible to different classes

of users

• Concurrent Access and Crash

Recovery – A DBMS schedules data access among various

users

– A DBMS protects against system failures

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Advantages of a DBMS

• Reduced Application Development

Times – A DBMS supports important data access

functions that are common to many applications

– A DBMS supports high-level interface to the

data

– DBMS applications are more robust

• No need for debugging and testing

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When NOT to Use a DBMS?

• A DBMS is complex

– Cost of DBMS

– Additional hardware costs

– Cost of conversion

– Higher impact of a failure

• Performance not adequate for certain applications

– Examples:

• Real-time constraints

• Critical constraints (need special custom code)

• Applications may need to manipulate data in ways not supported by query language

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Components of DBMS Environment

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Components of DBMS Environment

• Hardware – Can range from a PC to a network of

computers.

• Software – DBMS, operating system, network software

(if necessary) and also the application

programs.

• Data – Used by the organization and a description

of this data called the schema.

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Components of DBMS Environment

• Procedures – Instructions and rules that should be

applied to the design and use of the

database and DBMS.

• People – End-User

– Database Administrator (DBA)

– Application Developer

– .

– … etc

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Components of Database Systems

D

B

M

S

E

n

g

i

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e

Design Tools

Table Creation Tools

Form Creation Tools

Query Creation Tools

Report Creation Tools

Procedural Language

Compiler

Run Time

Form Processor

Query Processor

Report Writer

Procedural Language Run

Time

Database

Users’ Data

Metadata

Indexes &

Other System

Data

Application

Metadata

Database Contains

Developer

Application

Programs

Application

Programs

Users

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Components of the DBMS

• The Design Tools – Each DBMS comes with a set of tools to help in

creating tables, forms, reports, queries, etc.

– Design tools also allow users more control

through the use of programming language

interfaces.

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Components of the DBMS

• The Runtime Facilities – Developers design forms, reports, and queries.

However, they contain no data. The DBMS

Runtime facilities are responsible for retrieving

the relevant data from the database and

displaying it in the form, report, or query.

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Components of the DBMS

• The DBMS Engine – The DBMS Engine has direct access to the

physical database. Requests sent to the database (in the form of tables, rows, and columns) are intercepted by the DBMS Engine and sent to the operating system in terms of files and file offsets.

– The DBMS Engine is also responsible of transaction management, locking, and backup and recovery.