A 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. An application 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.