database architectures and the web

COMP1711 Database Modelling and Knowledge Engineering

Database Architecturesand the Web

Chapter 3

Chapter 3 - Objectives

• Components of a DMBS

• Multi-user DBMS Architectures

• Web services

• Distributed DBMSs

• Data Warehousing

• Oracle Architecture

Components of a DBMS

Components of Database Manager




• Web services




Multi-User DBMS Architectures

• Teleprocessing

• File-server

• Client-server

Teleprocessing

• Traditional architecture.

• Single mainframe with a number of terminals attached.

• Trend is now towards downsizing.

File-Server Architecture

DBMS on

each workstation

File-Server

• File-server is connected to several workstations across a network.

• Database resides on file-server.

• DBMS and applications run on each workstation.

• Disadvantages include:• Significant network traffic.

• Copy of DBMS on each workstation.

• Concurrency, recovery and integrity control more complex.

Traditional Two-Tier Client-Server

Applications


• Client (tier 1) manages user interface and runs applications.

• Server (tier 2) holds database and DBMS.

• Advantages include:• wider access to existing databases;

• increased performance;

• possible reduction in hardware costs;

• reduction in communication costs;

• increased consistency.

Three-Tier Client-Server

• Client side presented two problems preventing true scalability:• ‘Fat’ client, requiring considerable resources on client’s computer to run

effectively.

• Significant client side administration overhead.

• By 1995, three layers proposed, each potentially running on a different platform.


• 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 toimplement load balancing.

• Maps quite naturally to Web environment.

Multi-user DBMS Architectures

• N-tier architectures• Three-tier architecture can be expanded to n tiers

• Application servers• Hosts an application programming interface (API) to expose business

logic and business processes for use by other applications




• Web services




Distributed DBMS

Distributed DBMSs

• Distributed database• Logically interrelated collection of shared data physically distributed

over a computer network

• Distributed DBMS• Software system that permits the management of the distributed

database

Makes the distribution transparent to users

Distributed DBMSs

• Characteristics of DDBMS• Collection of logically related shared data

• Data split into fragments

• Fragments may be replicated

• Fragments/replicas are allocated to sites

• Sites are linked by a communications network

• Data at each site is controlled by DBMS

• DMBS handles local apps autonomously

• Each DBMS in one or more global app

Distributed Processing

A centralized database that can be accessed over acomputer network.

NOT a distribute

database!




• Web services




Architecture of a Data Warehouse

Data Warehousing

• Data warehouse• Consolidated view of corporate data

• Drawn from disparate operational data sources

• Range of end-user access tools capable of supporting simple to highly complex queries to support decision making

• Subject-oriented, integrated, time-variant, and nonvolatile




• Web services




database architectures and the web

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