1. Chapter 9  2000 by Prentice Hall. 9-1 Client/Server Computing

2.  2000 by Prentice Hall.9-2 Learning Objectives After studying this chapter, you will be able to:  Describe client/server computing and the reasons for its growth  Compare and contrast client/server and LAN environments  Identify some popular client/server applications  Summarize key advantages and disadvantages of client/server systems

3.  2000 by Prentice Hall.9-3 What Is a Client/Server System?  A system that links a client and server through networks. The client requests the server for a given service and the server provides the service if a predetermined set of conditions is met.

4.  2000 by Prentice Hall.9-4 Client/Server System The client computer sends a request for service to the server over a network. If the client’s request is appropriate, the server provides the service. Client Server Networks

5.  2000 by Prentice Hall.9-5 Interactions between Client and Server  A number of rules guide the interactions between a client and a server  When a server receives a request from a client, it checks to see if the client is authorized  A server can serve multiple clients at the same time and, conversely, a client may request services from multiple servers  Client processes are independent of server processes

6.  2000 by Prentice Hall.9-6 Dumb Terminal/Host Processing  A client/server situation in which the server does all the processing work.

7.  2000 by Prentice Hall.9-7 Dumb Server  A client/server situation in which the server does not do any processing but delivers the data or files to the requesting client, which does all the processing.

8.  2000 by Prentice Hall.9-8 Front-end Software  Software that resides on the client and accesses data and programs from the server and then presents it in a user- friendly format for client users.

9.  2000 by Prentice Hall.9-9 Back-end Software  Software that resides on the server and helps to manage and protect the data and other files on the server.

10.  2000 by Prentice Hall.9-10 Middleware  Software that helps the client communicate with the server to ensure the smooth functioning of different components in a client/server system.

11.  2000 by Prentice Hall.9-11 Uses of Front-end, Back-end, and Middleware Software Type of Software Who Uses Responsible for… Front-end Back-end Middleware End users Programmers, network administrators Users, programmers, network administrators Database management systems Network security Application integrity backups Disaster recovery User interfaces Application development tools Document management Data access Smooth communication between the client and server

12.  2000 by Prentice Hall.9-12 The Growth in Client/Server Computing  The ubiquity of PCs  The interest in corporate downsizing  The high cost of running and maintaining mainframes The rapid growth in client/server computing can be traced to three powerful forces:

13.  2000 by Prentice Hall.9-13 Client/Server Database Applications  Graphical user interface  Program to access data  Data  Database management system Client Server Network Client’s requests are sent using structured query language (SQL)

14.  2000 by Prentice Hall.9-14 Client/Server Database Applications (cont.)  Database  Transaction processing  An exchange between two entities  E-mail Various client/server applications:

15.  2000 by Prentice Hall.9-15 Advantages and Disadvantages of Client/Server Systems Advantages Data are readily accessible to decision makers Reduced operating costs Reduced system development and maintenance time Increased organizational responsiveness Disadvantages Resistance to change High training costs Extensive planning required Inadequate standards Susceptible to security violations

16.  2000 by Prentice Hall.9-16 Advantages of Client/Server Systems  Data Are Readily Accessible to Decision Makers  Timely information can often translate into tangible benefits, such as increased profits or reduced operating costs; and intangible benefits, such as greater customer satisfaction.

17.  2000 by Prentice Hall.9-17 Advantages of Client/Server Systems (cont.)  Reduced Operating Costs  In the long run, the cost of information processing may be cheaper for client/server systems than for mainframe systems, thereby lowering overall operating costs.

18.  2000 by Prentice Hall.9-18 Advantages of Client/Server Systems (cont.)  Reduced System Development and Maintenance Time  With proper planning and the necessary expertise, developers can create client/server systems more quickly and efficiently than mainframe applications.

19.  2000 by Prentice Hall.9-19 Advantages of Client/Server Systems (cont.)  Increased Organizational Responsiveness  Designing a client/server system often compels managers and employees to search for more efficient, more effective business practices.

20.  2000 by Prentice Hall.9-20 Disadvantages of Client/Server Systems  Resistance to Change  The transition from a mainframe environment to a client/server environment is fraught with obstacles. It is clear that the knowledge, experience, and expertise guiding these mainframe and client/server technologies are quite different.

21.  2000 by Prentice Hall.9-21 Disadvantages of Client/Server Systems (cont.)  High Training Costs  Users need extensive training to successfully use and manage client/server environments. Because these systems often change the dynamics of the business environment, training must be comprehensive and include both the business and the technology side.

22.  2000 by Prentice Hall.9-22 Disadvantages of Client/Server Systems (cont.)  Extensive Planning Required  A business must plan carefully and develop a strategic plan for a client/server system. Without a plan, the system becomes an ad hoc collection of systems that don’t integrate information and streamline business processes.

23.  2000 by Prentice Hall.9-23 Disadvantages of Client/Server Systems (cont.)  Inadequate Standards  Like any other new and evolving technology, client/server systems lack standardization in terms of system management, maintenance, and security, resulting in some reinventing of the wheel.

24.  2000 by Prentice Hall.9-24 Disadvantages of Client/Server Systems (cont.)  Susceptible to Security Violations  The security concerns associated with client/server systems are greater than those associated with other information systems because client/server systems are prone to security violations. The same features that make the client/server flexible, modular, open, and responsive also make it risky and vulnerable.

25.  2000 by Prentice Hall.9-25 Guidelines for Client/Server Success  Know Thy Business and Its Goals  A key question at the heart of successful client/server systems is “Why do we do what we do?”  Plan, Plan, Plan  The plan should identify the areas in the company that will lend themselves well to automation and then specify client/server technologies that will meet those automation needs.

26.  2000 by Prentice Hall.9-26 Guidelines for Client/Server Success (cont.)  Training Is the Key  Reengineering almost always precedes the development of client/server systems. As a result employees are faced not only with a new system but also with a new or a different way of doing business.  Make Sure the Data Has Integrity  Data are essential to good decision making. The best of systems is only as good as the data that go into it.

27.  2000 by Prentice Hall.9-27 Guidelines for Client/Server Success (cont.)  Establish Standards  What kind of hardware are we going to use for servers?  What kind of hardware are we going to use for clients?  What software will the company use to establish communications between clients and servers?  What kind of applications will run on the clients?