Over time, organizations found that this centralized environment caused severe backlogs both in application processing and development. Although data is displayed on the dumb terminal, the host computer makes all the decisions about how the data is to be presented.īecause these host machines were extremely expensive and maintenance costs were equally high, it made sense for an organization to centralize as much of its data and application logic as possible. The only processing provided by the terminal is sending keystrokes to the host and displaying data to the user. The terminal is referred to as dumb simply because it has no inherent processing power of its own. The user of the application interfaces with the data through a dumb terminal. The business logic tier and the data access tier reside centrally on the host. In this environment, virtually all the processing power exists on a central host machine. The original computing architecture was the mainframe or host-based architecture. It's informative to look back at where this all started. Typical client/server architecture.īefore client/server, two other important architectures ruled the world: mainframe, or host-based computing, and PC/LAN-based computing. A client might or might not have the ability to connect to multiple servers at once.įigure 1.1 shows a representation of a typical client/server database environment. The data that returns from the database engine to the client in response to a query.Īlthough it is not a requirement of the client/server model, in almost every case, a server allows many clients to connect to it at once. The term for the communication flowing from a client application to the SQL Server database engine. The server processes the query and sends back results.Īn application that connects to a server to make use of the service it provides.Īn application that makes available any kind of service for use by a client application. To use the service, each of these clients sends a query to the server. Each of these applications connects to the database engine and uses the engine's services in a different way. SQL Server client applications that ship with the product include the Query Analyzer, SQL Server Enterprise Manager, Profiler, SQL Agent, and even Data Transformation Services.
Internet Explorer is a client that connects to a Web server. These applications connect to a mail server to retrieve e-mail messages. Some examples of client responsibilities are providing a pleasing user interface, making use of the limited server resources in a responsible and resource-economical way, and, of course, fulfilling the goals of the application.Ĭlient applications include mail clients, such as Eudora and Microsoft Outlook.
Some examples of server responsibilities are providing backups to ensure data is safe, security against unwanted intrusion, timely access to the service, and maintenance of reliable storage facilities to ensure high availability of the service. A client is an application that connects to a server to make use of the service it provides.Ĭlients and servers have different jobs. In the simplest terms, a server is a program that makes available any kind of service, such as e-mail, files, ftp, Web, or data in the form of a database server. Client/server is a style of computing where a client process requests services from a server process.