Publishing Reports to the Web - Downloads - Oracle

Methodology
20.1.3 Formatting the Data
SELECT d.dname, e.ename
FROM emp e, dept d
WHERE e.deptno(+) = d.deptno
■ Two queries with a column link based on deptno
SELECT deptno, dname FROM dept
SELECT deptno, ename FROM emp
When you design the data model in the report, minimize the actual number of queries
by using fewer large multi-table queries, rather than several simple single-table
queries. Every time a query is run, Oracle Reports needs to parse, bind, and execute a
cursor. A single query report returns all the required data in a single cursor, rather
than many cursors. With master-detail queries, the detail query will be parsed, bound,
and executed again for each master record retrieved. In this example, it is more
efficient to merge the two queries and use break groups to create the master-detail
effect.
Keep in mind that the larger and more complex a query gets, the more difficult it is to
be maintained. You need to decide when to achieve the balance between performance
and maintenance requirements.
After the data is retrieved from the data source, Oracle Reports generates the report
layout and formats the output. The time taken for a paper layout depends on a
number of factors, but generally comes down to:
■ The work required to prevent an object from being overwritten by another object.
■ The efficiency of any calculations or functions performed in the format triggers.
The rules for a Web layout are a little different as Oracle Reports does not:
■ Own the Web page
■ Control the rendering mechanism
It merely injects data into a regular JSP page.
20.1.3.1 Paper Layout
When generating a default paper layout, Oracle Reports wraps a frame around
virtually every object to prevent the objects from being overwritten, when the report is
run. At runtime, every layout object (frames, fields, boilerplate, etc.,) is examined to
determine the likelihood of that object being overwritten. In some situations (for
example, boilerplate text column headings) when there is clearly no risk of the objects
being overwritten, the immediately surrounding frame is removed. This reduces the
number of objects that Oracle Reports must format and consequently improves
performance.
Extra processing is required when an object has an undefined size (variable,
expanding, or contracting either horizontally and / or vertically). In this case, Oracle
Reports must determine the instance of the object's size, before formatting that object
and those around it. There is no processing overhead involved for objects assigned a
fixed size, as the size and positional relationships between the objects is known.
The following guidelines helps to improve performance when creating a paper layout:
■ Make your non-graphical layout objects (for example, boilerplate text or fields
with text) fixed in size by setting the Vertical Elasticity and Horizontal Elasticity
properties of the field to Fixed. In particular, setting the size of repeating frames
20-12 Oracle Application Server Reports Services Publishing Reports to the Web