2.Oracle Client/Server Architecture: Distributed Processing

Distributed processing uses more than one processor to divide the processing for a set of related jobs. Distributed processing reduces the processing load on a single processor by allowing different processors to concentrate on a subset of related tasks, thus improving the performance and capabilities of the system as a whole.

An Oracle database system can easily take advantage of distributed processing by using its client/server architecture. In this architecture, the database system is divided into two parts: a front-end or a client and a back-end or a server.

The Client

The client is the front-end database application and is accessed by a user through the keyboard, display, and pointing device such as a mouse. The client has no data access responsibilities. It concentrates on requesting, processing, and presenting data managed by the server. The client workstation can be optimized for its job. For example, it may not need large disk capacity or it may benefit from graphic capabilities.

The Server

The server runs Oracle software and handles the functions required for concurrent, shared data access. The server receives and processes the SQL and PL/SQL statements that originate from client applications. The computer that manages the server can be optimized for its duties. For example, it can have large disk capacity and fast processors.

Multitier Architecture: Application Servers

multitier architecture has the following components:

  • A client or initiator process that starts an operation
  • One or more application servers that perform parts of the operation. Anapplication server provides access to the data for the client and performs some of the query processing, thus removing some of the load from the database server. It can serve as an interface between clients and multiple database servers, including providing an additional level of security.
  • An end or database server that stores most of the data used in the operation

This architecture enables use of an application server to:

  • Validate the credentials of a client, such as a web browser
  • Connect to an Oracle database server
  • Perform the requested operation on behalf of the client

The identity of the client is maintained throughout all tiers of the connection. The Oracle database server audits operations that the application server performs on behalf of the client separately from operations that the application server performs on its own behalf (such as a request for a connection to the database server). The application server's privileges are limited to prevent it from performing unneeded and unwanted operations during a client operation.