Multi-tiered Database Applications
Go Up to Database Architecture
In multi-tiered database applications, an application is partitioned into pieces that reside on different machines. A client application provides a user interface to data. It passes all data requests and updates through an application server (also called a “remote data broker”). The application server, in turn, communicates directly with a remote database server or some other custom dataset. Usually, in this model, the client application, the application server, and the remote database server are on separate machines. The Following illustrates these relationships for multi-tiered applications.
You can use Delphi to create both client applications and application servers. The client application uses standard data-aware controls connected through a data source to one or more client dataset components to display data for viewing and editing. Each client dataset communicates with an application server through an IProvider interface that is part of the application server’s remote data module. The client application can use a variety of protocols (TCP/IP, DCOM, MTS, or CORBA) to establish this communication. The protocol depends on the type of connection component used in the client application and the type of remote data module used in the server application.
The application server creates the IProvider interfaces in one of two ways. If the application server includes any provider objects, then these objects are used to create the IProvider interface. This is the method illustrated in the previous figure. Using a provider component gives an application more control over the interface. All data is passed between the client application and the application server through the interface. The interface receives data from and sends updates to conventional datasets, and these components communicate with a database server.
Usually, several client applications communicate with a single application server in the multi-tiered model. The application server provides a gateway to your databases for all your client applications, and it lets you provide enterprise-wide database tasks in a central location, accessible to all your clients. For more information about creating and using a multi-tiered database application, see Creating multi-tiered applications in the in the Delphi Developer’s Guide.