02-06-2012, 02:18 PM
Client/Server Computing
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Why Client/Server ?
The business environment of the 1990's is rapidly changing. Corporate organizations are flattening their organization structures to be more responsive to customers and the marketplace. Traditional competitors are now cooperating with one another while competing at the same time in different markets. Key competitive advantages are characteristics like time-to-market, customer service and simplicity. Being first to a market with a quality product or service which delights customers can be the difference between market success or failure. Time to market is now measured in weeks not years, and being first may be the only advantage one company has over its competitors. Customer service means delighting the customer with both a product or service as well as being responsive to changing customer requirements. Organizational structures are flattening in order to empower employees to make decisions closer to the customer, to be more responsive to the customer. Personal computers provide a whole new level of computing flexibility, with simple easy to use programs. These programs are transportable, allowing businesses to react instantly to customers needs. Simplicity, to the end user, is critical to the success of client/server computing. End users need information access as easy as getting cash from an automated teller machine (ATM). Customers can get money from their bank account at any ATM across the country with just an ATM card and a password. Client/server computing means changing our information systems to support the changes of the business environment. Lets look at an analogy.
Client/Server Analogy
Restaurant service is an analogy to help explain client/server computing. The customer (client) makes a series of requests for a specific set of services that may include an appetizer, beverage, main course and a dessert. These requests are all typically made to one person, the waiter (server). The services may actually be provided by a number of other people in the restaurant including the bus boy, bartender, and a variety of chefs. However, to the customer, these services are all provided by one person, the waiter. The customer doesn't want to know who performs what service. He would just like to have a high quality meal delivered in a timely fashion. The client, in client/server computing is much like the customer in a restaurant. The client requests a service, like running an application or accessing some information from a data base. The server becomes responsible for performing the service and returning the information to the client in a timely manner. The server is like the waiter in a restaurant responsible for handling the client's requests and delivering the finished product to the client.
Client/Server Definition:
Client/server computing provides the seamless integration of personal computers with host systems. This style of computing allows organizations to be responsive to their customers while still maintaining the security and integrity to manage their business effectively. Client/server computing generally refers to a computing model where two or more computers interact in such a way that one provides services to the other. This model allows customers to access information resources and services located anywhere within the customers information network. Customers are very interested in client/server computing because it allows them to be more responsive, as well as to effectively utilize all computing resources within their network.
As the term implies, client/server computing has two basic components, a client and a server. The client requests a service to be performed. This service might be to run an application, query a data base, print a document, or even perform a backup or recovery procedure. The server is the resource that handles the client's request. Clients are typically thought of as personal computers but a client can be a midrange system or even a mainframe. Servers are typically thought of as a midrange or mainframe system, however a server can be another personal computer on the network. Client/server networks are like our restaurant example where specific computers provide one or more services to other computers within a network. Today's networks have computers for file serving, data base serving, application serving, and communications serving. Each of these servers are dedicated devices which provide a specific service to all authorized users within a network. These servers also allow some of the processing to be handled on each users PC and some on a centralized server, as the picture below shows.
Client/Server Definition
For example, a data base server uses the PC for the display (user interface) and processing (application logic) portions of an application, while the server provides data management portion of the application. On the other hand, an application server uses the PC for the display portion of an application, while using the server for both the processing and data management portions.
Data Base and Application Server
Each of these models is best suited for specific types of applications and most customers make use of different application models based upon the business need being satisfied. This workload separation allows small servers to handle a larger number of users. In a rapidly changing business environment client/server computing offers customers the flexibility they need to manage their business effectively.