Oracle Application Express installs with your Oracle database and is comprised of data in tables and PL/SQL code.
Whether you are running the Oracle Application Express development environment or an application you built using Oracle Application Express, the process is the same. Your browser sends a URL request that is translated into the appropriate Oracle Application Express PL/SQL call. After the database processes the PL/SQL, the results are relayed back to your browser as HTML. This cycle happens each time you either request or submit a page.
The application session state is managed in the database tables within Application Express. It does not use a dedicated database connection. Instead, each request is made through a new database session, consuming minimal CPU resources.
The version of Oracle Database you use determines how the URL is translated:
Versions prior to Oracle Database 11.1 require Oracle HTTP Server (Apache) with
mod_plsql. The following graphic illustrates the three-tier architecture
With Oracle Database 11.1 or later or Oracle Database 10g Express Edition, you can remove Oracle HTTP Server and
mod_plsql from the architecture and replace it with the embedded PL/SQL gateway. The following graphic illustrates the two-tier architecture using the embedded PL/SQL gateway.
The embedded PL/SQL gateway provides the Oracle database with a Web server and also the necessary infrastructure to create dynamic applications. The embedded PL/SQL gateway runs in the XML DB HTTP server in the Oracle database and includes the core features of
mod_plsql, but does not require the Oracle HTTP Server powered by Apache. Inclusion of the embedded PL/SQL gateway simplifies the architecture and eliminates the middle tier entirely.
The Application Express engine renders and processes pages. It also performs these tasks:
session state management
page flow control
When you install Oracle Application Express, you can install two different environments: