What is Distributed Application Processing?
• two-tier application processing architecture
• three-tier application processing architecture
The vast majority of Oracle applications are distributed processing applications. With distributed application processing, the components of an application's functionality are distributed and executed by two or more computers in a network.

Understanding Two-Tier Application Processing

A two-tier or client/server database application architecture is one in which the user interface runs on a client and a data management component executes on a server.
• The client is the front end of a database application. The client is the visible interface that an application user works with to input, retrieve, and analyze data. The client portion of a client/server database application typically executes on a PC or workstation. In an Oracle database environment, applications such as SQL*Plus, Oracle Financials, custom forms and reports developed with tools such as Oracle Developer (Oracle Forms and Oracle Reports) and Oracle Designer, and common Web browsers are all examples of clients.
• The server is the back end of a database application. The database server's job is to manage shared database access among multiple, possibly many, concurrent application users. For example, when an application submits a query, a client process sends the query to a server process, which then retrieves the requested data from the database to send back to the client. To deliver acceptable performance and store its associated databases, a database server computer usually has one or more fast processors, a lot of physical memory (RAM), and a significant amount of disk storage.
• When the client and server portions of a database application operate on different computers, a network is necessary so that the different computers can communicate. Additionally, two computers that want to communicate directly with each other must speak a common language, or communications protocol. A network protocol is software that defines a common set of rules and signals that computers on the network use to communicate with each other. The most common network protocols in use today are TCP (Transmission Control Protocol) and IP (Internet Protocol), which typically work together as TCP/IP.
Understanding Three-Tier Application Processing

A three-tier application processing architecture is a variant of the client/server architecture and consists of three well-defined and separate application processes, each running on a different node in a network.
• The user interface executes on the user's computer (the client).
• The functional application modules that process data execute on a middle tier server. This component is often called the application server. The application server assumes the identity of a client when it is performing operations on the database server for the client. The middle tier might also serve as a gateway or a bridge to link different networks. In Oracle environments, the middle-tier is typically the Oracle9i Application Server.
• The data management component, Oracle, executes on a separate server.
The three-tier design has several advantages over traditional two-tier designs, including:
• The added modularity makes it easier to modify or replace one tier without affecting the other tiers.
• Separating the application functions from the database functions makes it easier to balance the load among available servers and communications channels.
The Benefits of Distributed Application Processing
• efficient database application development
• optimal performance
Tiered application processing architectures are common because they provide important benefits:
• A single back-end database management component, or database server, can support any number of front-end client applications. Consequently, you can build many database applications efficiently, without having to build and test a data management component for each application.
• The individual clients and server component of the application can all run on different computers that communicate using a network. Consequently, you can distribute the overall processing requirements of the application among several computers rather than overload a single computer.

Good concepts Priyan. Please go through attachment about the Distributed Application Architecture and also visited the link for creating the distributed application.

-V.Vadivelan

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