Introduction To Databases Transparencies: © Pearson Education Limited, 2004 1
Introduction To Databases Transparencies: © Pearson Education Limited, 2004 1
Introduction To Databases Transparencies: © Pearson Education Limited, 2004 1
Chapter 1 - Objectives
Common uses of database systems. Meaning of the term database. Meaning of the term Database Management System (DBMS). Components of the DBMS environment. Typical functions of a DBMS. Advantages/disadvantages of DBMSs.
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Purchases from the supermarket Purchases using your credit card Booking a holiday at the travel agents Using the local library Renting a video Using the Internet
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Database
Shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization.
Database
Shared collection can be used simultaneously by many departments and users. Logically related - comprises the important objects and the relationships between these objects. Description of the data the system catalog (meta-data) provides description of data to enable data independence. Pearson Education Limited,
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DBMS
A software system that enables users to define, create, and maintain the database and that provides controlled access to this database.
A software program that interacts with the database by issuing an appropriate request (typically an SQL statement) to the DBMS.
Views
Allows each user to have his or her own view of the database. A view is essentially some subset of the database.
Views
Benefits include:
Provide a level of security; Provide a mechanism to customize the appearance of the database; Present a consistent, unchanging picture of the structure of the database, even if the underlying database is changed.
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DBMS
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Hardware
Can range from a PC to a network of computers. DBMS, operating system, network software (if necessary) and also the application programs. Used by the organization and a description of this data called the schema.
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Software
Data
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Procedures
Instructions and rules that should be applied to the design and use of the database and DBMS.
People
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Two-Tier Client-Server
Client manages main business and data processing logic and user interface. Server manages and controls access to database.
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Two-Tier Client-Server
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Fat client, requiring considerable resources on clients computer to run effectively. Significant client side administration overhead.
User interface layer runs on client. Business logic and data processing layer middle tier runs on a server (application server). DBMS stores data required by the middle tier. This tier may be on a separate server (database server).
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Advantages:
Thin client, requiring less expensive hardware. Application maintenance centralized. Easier to modify or replace one tier without affecting others. Separating business logic from database functions makes it easier to implement load balancing. Maps quite naturally to Web environment.
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Functions of a DBMS
A User-Accessible Catalog.
Transaction Support. Concurrency Control Services. Recovery Services.
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Functions of a DBMS
Authorization Services.
Support for Data Communication.
Integrity Services.
Services to Promote Data Independence.
Utility Services.
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Advantages of DBMSs
Control of data redundancy Data consistency Sharing of data Improved data integrity Improved maintenance through data independence.
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Disadvantages of DBMSs
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