The
???client??? process becomes the middle tier, or application server.
Youcan logically consider any process that connects to an Oracle instance a client in
the sense that it is served by the database. Don??™t confuse this usage of the term client
with the actual client in a multitier configuration. The eventual client in a multitier
model is some type of program providing a user interface??”for example, a browser
running Java.
The Oracle Application Server, which is part of the overall Oracle platform, is
designed to act as this middle tier. Application Server works seamlessly with the Oracle
database and shares some of the same technology. Application Server is described
in more detail in Chapter 15.
Figure 3-5 illustrates users connecting to an Oracle instance to access a database in
both two-tier and three-tier configurations, involving local and network communication.
This figure highlights the server process connection models as opposed to the
interaction of the background processes. There is a traditional two-tier client/server
connection on the left side, a three-tier connection with an application server on the
right side, and a local client connection in the middle of the figure.
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