Applications Tier
The applications tier is responsible for storing and
executing most of the business logic associated with R12. It also provides all
the non-database services required in an R12 instance (for example, Web
listeners, Forms servers, Reports servers, Concurrent Processing, and so on).
The application tier is the key tier consisting of a host of services within
the R12 architecture.
It is simpler to state that all components that are not part
of either the desktop tier (that is, Forms display) or the database tier are
assigned to the applications tier.
Prominently, six servers comprise the application tier for
Oracle Applications:
Web server: The Oracle HTTP
Server (powered by Apache) acts as the Web server. It processes the requests
received over the network from the desktop clients, and includes additional
components such as:
Web Listener
Java Servlet Engine
JavaServer Pages (JSP)
The Web Listener component of the Oracle HTTP Server accepts
incoming HTTP requests (for particular URLs) from client browsers.
Forms server: The Forms
server hosts the Oracle Applications forms and associated run-time engine that
supports the professional interface. It is a component of the Oracle Developer
6i, which mediates the communication between the desktop client and the
Oracle database server, displaying client screens and initiating changes in the
database according to user actions. It caches data and provides it to the
client as required—for example, when scrolling through multiple order lines
that exceed the limitations of a single screen. The Forms server communicates
with the desktop client using these protocols:
Standard HTTP network connection
Secure HTTPS network connection
TCP/IP connection
Reports server: The Reports
server is automatically installed on the same node as the Concurrent Processing
server, and its reports are contained in the same directory as the concurrent
processing reports. However, reports generated by the Reports server are
monitored and administered separately from the concurrent processing reports.
It dynamically selects the language of the report at run time, so that users
see the reports in the language they prefer.
Discoverer server (optional):
The Discoverer server complements the Reports server by allowing performance of
ad hoc queries and analysis of the resulting query output. It also allows users
to perform projections based on possible changes to the business environment or
other strategic factors.
Concurrent Processing server:
User interactions with Oracle Applications data are conducted via HTML-based
Applications or the more traditional Forms-based Applications. However, there
are reporting programs and data update programs that need to run either
periodically, or on an ad hoc basis. These programs that operate in the
background while users continue to work on other tasks, may contain a large
number of data-intensive computations, and run using the concurrent
processing architecture. To ensure that resource-intensive concurrent
processing operations do not interfere with interactive operations, they are
run on a specialized server, the Concurrent Processing server. Processes
that run on the concurrent processing server are called concurrent requests.
Administration server: The
Administration server is located on the node on which you maintain the data
model and the data in your Oracle Applications database. You carry out the
following operations from this server:
Upgrading Oracle Applications
Applying database patches to Oracle
Applications
Maintaining Oracle Applications
data
Note: The Oracle HTML-based (formerly known as
Self-Service) Applications:
Do not use Oracle Forms for the
interface
Are designed in pure HTML and
JavaScript
Dynamically generate HTML pages by
executing Java code
Use a metadata dictionary for
flexible layout
Operate by direct connection to
the Web server
