ClientServer Systems

1
Chapter 12

• Client/Server Systems
• Database Systems Design, Implementation, and
  Management, Fifth Edition, Rob and Coronel

2
In this chapter, you will learn

• What client/server computing is
• What the advantages of using client/server
  systems are
• How client/server systems evolved
• About client/server systems components and how
  they interact
• What effect the client/server system has on the
  DBMS
• How client/server systems might be introduced
  into an organization
• What factors affect the implementation of
  client/server systems

3
Client/Server Computing

• Computing model for the development of
  computerized systems
• Client requests specific service
• Server provides requested service
• Reside on same or different computers

Figure 12.1
4
Client/Server Computing (cont.)

• Key to client server power is where request
  processing takes place
• Extent of sharing processing
• Thin client
• Thin server
• Fat client
• Fat server
• Classification
• 2-tier
• 3-tier

5
Forces that Drive Client/Server Trend

• Changing business environment
• Growing need for enterprise data access
• Demand for end-user productivity gains based on
  efficient use of data
• Technological advances
• Growing cost/performance advantages

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Mainframe vs. Client/Server Systems
Table 12.1
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Components of Client/Server Architecture

• Client
• Front-end application
• Server
• Back-end application
• Communications middleware
• Communications layer

Figure 12.3
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Example Client/Server Architecture
Figure 12.4
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Client/Server Principles

• Hardware independence
• Software independence
• Operating systems
• Network systems
• Applications
• Open access to services
• Process distribution
• Process autonomy
• Maximization of local resources
• Scalability and flexibility
• Interoperability and integration
• Standards

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Server Components

• File services
• Print services
• Fax services
• Communications services
• Database services
• Transaction services
• Miscellaneous services

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Server Components
Figure 12.6
12
Server Process Benefits

• Location independence
• Resource optimization
• Scalability
• Interoperability and integration

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Database Middleware

• Network independence
• Front-end application accesses data without
  regard to network protocols
• Database server independence
• Generic SQL to access different database servers
• Isolates programmer from SQL dialect differences

14
Communications Middleware

• Two levels
• Physical level
• Client and server computers
• Logical level
• Client and server processes
• Interprocess communication (ICP) protocols

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Database Middleware Components
Figure 12.9
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Interactions between Middleware Components
Figure 12.10
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Middleware Accessing Multiple Database Servers
Figure 12.11
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Middleware Accessing Mainframe Databases
Figure 12.12
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Middleware Classifications

• Messaging-oriented middleware (MOM)
• Remote-procedure-call-based (RPC-based) middle
  ware
• Object-based middleware

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Competing Standards

• Client operating systems
• Microsoft Windows
• OS/2, Apple Mac OS, Unix, Linux
• Client graphical user interfaces
• Microsoft Windows
• OS/2 Presentation Manager, Macintosh, UNIX
• Server operating systems and network protocols
• Database servers Unix, OS/2, Windows NT
  Server/2000 Server
• Printer and file servers Novell Netware
• LAN protocols TCP/IP, IPX/SPX, NetBIOS
• Middleware
• ODBC, IDAPI, DRDA, QE

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Client/Server DBMS Functions

• Transparent data access to multiple,
  heterogeneous clients
• Allow client requests to the database server over
  network
• Process client data requests at local server
• Send only SQL results to clients over network

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Application Logic Components
Figure 12.14
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Client/Server Architectural Styles

• Two Key Questions
• How is the division made?
• Where should the results of division be placed?
• Five Functional Logic Components
• Presentation logic
• I/O processing logic
• Application of business logic
• Data management logic
• Data manipulation logic

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Application Functional Components
Figure 12.15
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Functional Logic Splitting
Figure 12.16
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Client/Server Implementation Issues

• Management Issues
• Communications infrastructure
• Applications
• Controlling escalating and hidden costs
• People and cultural changes
• Multiple vendor relationships
• Development tool acquisition
• Determination if client/server approach is
  correct