Operation Manual

Designing Optimized Web Reports
Making the right design choices
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Crystal Reports User’s Guide 135
processes scheduled reports against the database, and the Page Server
processes on-demand reports against the database. The Page Server
also formats individual pages of report instances when users view them.
• When a scheduled report is processed, all date and time formulas are
evaluated by the Job Server in order to generate the report instance.
When you simply view the resultant report instance, none of the formulas
is re-evaluated.
• When you view a cached report page, none of the date functions is re-
evaluated, because the records have already been read and the page
has already been formatted.
• If you use date and/or time functions in a report’s selection formula, the
report’s data is dependent upon the return values of those formulas.
Consequently, when you view a report instance at a later date, the
function may cause the report data to be updated from the database.
• To ensure that date and time functions return the values that you expect, you
can force the evaluation time through the use of the WhileReadingRecords
and WhilePrintingRecords functions. For more information, see the
“Functions” and “Report Processing Model” sections of the Crystal Reports
Online Help.
Making the right design choices
This section offers design options and considerations that will help improve
the performance of your reports. The topics covered range from basic
suggestions, such as updating reports created in older versions of Crystal
Reports to the latest file format, to more involved decisions, such as whether
to use live or saved data, and how to use subreports efficiently.
When designing your reports, and especially when designing reports for the
Web, you should allow report users to drive the data they see. In other words,
display summarized information, so each user can navigate the report quickly
and then drill down to access additional data. In this way, web traffic and
response times are minimized, because only the data requested by the user
is transferred from the database server.
These are only a few of the benefits of designing user-driven reports:
• Report users gain interactive control over the type and quantity of
information they view over the Web.
• Data transfer and network traffic decrease, because only the information
requested by users is returned from the database server.