Concepts of Database Concepts of Database Management, Fifth Management, Fifth

EditionEdition

Chapter 9:Chapter 9:

Database Management Database Management ApproachesApproaches

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Objectives

Describe distributed DBMSs

Discuss client/server systems

Define data warehouses and explain their structure and access

Discuss the general concepts of object-oriented DBMSs

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Objectives

Summarize the impact of Web access to databases

Provide a brief history of database management

Describe the network and hierarchical data models

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Distributed Databases

Computers at various sites

Connected with communications network

Distributed database is single logical database physically divided among networked computers

DDBMS supports and manipulates distributed databases

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Figure 9.1: Communications Network

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Characteristics ofDistributed DBMSs

Homogeneous

Same local DBMS at each site

Heterogeneous

At least two sites with different DBMSs

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Characteristics ofDistributed DBMSs (con’t.)

Location transparency User feels as though entire database is at their

site

Replication transparency User unaware of behind the scenes replication

of the data Fragmentation transparency

Logical object divided among various locations

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Unfragmented Parts Table

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Fragmented Parts Table

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Advantages of Distributed Databases

Local control of data Possible legal reasons for local control over data

used in a particular geographic region Increased database capability Added system availability

Though parts of a database may not be accessible, transactions can still occur, increasing overall availability of the database

Added efficiency Smaller tables are faster to query

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Disadvantages of Distributed Databases

Problems updating replicated data

More complex query processing

More complex treatment of concurrent update

More complex recovery measures

More difficult management of the data dictionary

More complex database design

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Rules for Distributed Databases Local autonomy

No reliance on a central site

Continuous operation

Location transparency

Fragmentation transparency

Replication transparency

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Rules for Distributed Databases (con’t.)

Distributed query processing

Distributed transaction management

Hardware independence

Operating system independence

Network independence

DBMS independence

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Client-Server Systems

Tiered approach to developing systems

Typical systems will implement two tiers Client

Server

Server manages all access to data

Client consults server for most processing

Some systems almost totally abstract the client from any processing by introducing a middle tier to handle all logic or processing

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Figure 9.4: Client/Server Systems

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Figure 9.5: Two-Tier Client/Server Architecture

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Figure 9.6: Three-Tier Client/Server Architecture

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Advantages ofClient/Server Systems

Lower network traffic

Improved processing distribution

Thinner clients

Greater processing transparency

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Advantages ofClient/Server Systems (con’t.)

Increased network, hardware, and software transparency

Improved security

Decreased costs

Increased scalability

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Triggers and Stored Procedures

Triggers Actions that occurs automatically in response

to a particular database operation

Created by programmers

Use special SQL statements

Stored Procedures Collection of SQL statements compiled and

optimized by DBMS

Improves performance

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Data Warehouses

Subject-oriented, integrated, time-variant, nonvolatile collection of data in support of management’s decision-making process

Used for analysis of existing data

Resolves performance issues suffered by operational RDBMSs and OLTPs

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Figure 9.7:Data Warehouse Architecture

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Figure 9.8:Data Warehouse Structure

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On-Line Analytical Processing

Optimized to work with data warehouses

Used to answer questions

Allows users to perceive data as a multidimensional data cube

Slice and dice

Drill down

Roll Up

Data mining

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Figure 9.9: Data Cube Representation

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Figure 9.11: Slicing on Time Dimension

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Figure 9.12: Dicing on Part Dimension

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Rules for OLAP Systems

Multidimensional conceptual view

Transparency

Accessibility

Consistent reporting performance

Client/server architecture

Generic dimensionality

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Rules for OLAP Systems

Dynamic sparse matrix handling

Multiuser support

Unrestricted, cross-dimensional operations

Intuitive data manipulation

Flexible reporting

Unlimited dimensions and aggregation levels

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Object-Oriented DBMS (OODBMS)

System in which data and methods operating on that data are encapsulated into objects

Store graphics, drawings, video, sound, and other complex objects called binary large objects (BLOBs)

General concepts Objects and classes

Methods and messages

Inheritance

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Unified Modeling Language (UML)

Models various aspects of software development for OO systems

Includes several types of diagrams Class Use Case State Sequence Activity Collaboration Component

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Figure 9.19: Class Diagram for Premiere Products

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Figure 9.20: Class Diagram with Constraints

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Figure 9.21:Class Diagram with a Generalization and a Constraint

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Rules for OODBMSs

Complex objects

Object identity

Encapsulation

Information hiding

Types of classes

Inheritance

Late binding

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Rules for OODBMSs (con’t.)

Computational completeness

Extensibility

Persistence

Performance

Concurrent update support

Recovery support

Query facility

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Web Access to Databases

Electronic Commerce

Conducting business on the Internet

Business to Business

Business to Consumer

Internet facilitating better access to data

Extensible Markup Language (XML)

Key technology to data interchange between systems

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Figure 9.22: Web Access to Databases

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History of Database Management

Early systems

GUAM, DL/I, IMS, IDS, IDMS

Relational products

DB2, Oracle, Sybase, Paradox, dBASE, Access, MySQL, SQL Server

OODBMSs

Gemstone, Objectivity/DB, Versant

ORDBMSs

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Hierarchical and Network Databases

Data models have two components, structure and operations Structure is how users perceive data to be

structured Operations are facilities given to users to interact

with data Users perceive a network model database as a

collection of record types and relationships Users perceive a hierarchical model as a

collection of hierarchies or trees

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Summary Distributed databases physically fragment a

database across many parts of a DBMS, but they must maintain reasonable transparency

Most applications built around a DBMS will use a client-server architecture, involving at least two tiers, but more typically three

Data warehouses are specialized DBMS products that allow users to view the data in more than two dimensions, typically three

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Summary (con’t.)

Object Oriented databases provide an encapsulated view by merging data with their operations, fitting with modern programming architectures

Web access is common way to access data in a DBMS

Hierarchical and network data models are two models of how users perceive a DBMSs structure and operation