Publishing Reports to the Web - Downloads - Oracle

Methodology
and their contents to fixed, improves performance. Variable (size) non-graphical
objects require more processing overhead, because Reports Builder must
determine their size before formatting them. However, the overhead for fixed
non-graphical objects is less, since the additional processing is not required.
■ Make your graphical layout objects (for example, images and graphs) variable in
size by setting the Vertical Elasticity and Horizontal Elasticity properties of the
objects to Variable. Fixed graphical objects require more processing overhead as
their contents have to be scaled to fit. Variable objects grow or shrink with the
contents eliminating the need for scaling.
■ Make text fields span a line (maximum) and ensure that their contents fit within
the specified width (for example, use the SUBSTR function). If a text field spans
more than a line, Reports Builder must use its word wrapping algorithm to format
that field. Ensuring the text field takes only one line to format avoids the
processing overhead of the word wrapping algorithm.
■ Minimize the use of different formatting attributes (for example, fonts) within the
same field or boilerplate text, because it takes longer to format.
■ Use the SUBSTR function in the report query to truncate the data at the database
level, instead of truncating a character string from a field in the Report Builder
layout.
■ For paper layout only reports, .rdf and .rep files run faster than a.jsp file,
because the serialized formats of a .rdf or a .rep file do not require parsing.
Additionally, a .rep file runs faster than a .rdf file as it is optimized for the
current platform.
20.1.3.1.1 Format Triggers in a Paper Layout Format triggers can dynamically disable,
enable, and change the appearance of an object. Exercise caution when using them as
they fire each time an instance of their associated object is produced and formatted (at
runtime).
Consider the following example, on the use of format triggers:
A tabular report includes a single repeating frame that expands vertically and has the
Page Protect property set to On. As the report is formatted, there is room for one more
line at the bottom of the first page. Oracle Reports starts to format the next instance of
the repeating frame and fires its associated format trigger. One of the objects inside the
repeating frame is found to have expanded and this instance of the repeating frame is
moved to the following page. The format trigger for the repeating frame is fired again.
Although the repeating frame only appears once (at the top of the second page), the
format trigger has fired twice. DML should not be performed in a format trigger,
because you are not sure how many times the format trigger will fire for a particular
object.
With the example above, had the format trigger contained an INSERT statement, then
two rows of data would have been inserted.
Format triggers can be used against repeating frames to filter data. However, by
introducing filtering at appropriate levels, you not only improve a report's
performance but also reduce the complexity required for this type of a report.
Use the following filtering order whenever possible:
■ Modify the SQL statement to prevent the data being returned from the server.
■ Use the group filter to introduce filtering in the Data Model.
■ Use return false inside the format trigger.
Tuning Oracle Reports 20-13