Before looking at any particular SAP Crystal
Reports product or architecture, it is useful to view an abstract reporting
model to identify several logical components of a reporting application.

The report viewer renders a report source into
DHTML and provides interaction controls, such as Search, Zoom, Drill Down,
Export, and Print.
Report sources
A report source is an object used by the viewer
to access the properties of a report. It provides the viewer with the means to
query for report data, page information, and other internal report information.
Report sources are obtained from report servers such as the Crystal Reports
2011 Processing Server and the Crystal Reports 2011 Report Application Server.
Choosing a report server
Although some applications that you develop may
work equally well using the Crystal Reports 2011 Processing Server or the
Crystal Reports 2011 Report Application Server, there are likely to be
situations when the requirements of a particular application mean that you must
use one type of report server instead of the other.
In general, the Crystal Reports 2011 Report
Application Server provides greater functionality over the Crystal Reports 2011
Processing Server, including such features as the ability to schedule reports,
receive alerts, and make runtime changes to reports. However, running reports
through the Crystal Reports 2011 Processing Server provides greater scalability
because once a report on the Crystal Reports 2011 Processing Server has been
viewed by one user, a copy of it is kept on the Crystal Reports Cache Server,
providing quick access to the same report by hundreds of other users.
When to use a
Crystal Reports 2011 Processing Server as your report server
You should choose to access your Crystal
reports through a Crystal Reports 2011 Processing Server when any of these
conditions are true:
You are using the viewers within an SAP
BusinessObjects Business Intelligence platform environment and do not have the Crystal Reports 2011
Report Application Server running.
You wish to take advantage of the Crystal
Reports 2011 Processing Server's interaction with the Crystal Reports Cache
Server, so that individual report pages are not generated every time they are
requested.
Your application delivers reports that do
not need to be changed at run-time.
When to use a
Crystal Reports 2011 Report Application Server as your report server
You should choose to access your Crystal
reports through a Crystal Reports 2011 Report Application Server when any of
these conditions are true:
Your application needs to display reports
that it has opened for modification on the Crystal Reports 2011 Report
Application Server.
Your application accesses Crystal report
files (.rpt files) directly from a file system. This
functionality is only provided by an unmanaged Crystal Reports 2011 Report
Application Server.
A report source served by a Crystal Reports
2011 Report Application Server can be used to modify report elements
programatically, using the Report Application Server SDK. For example,
depending on a user’s preferences, your application can apply a template to an
existing report.