24.6 General Layout Guidelines

This section outlines guidelines that you can follow when designing your report's layout to improve performance:

24.6.1 Fetching Ahead

Oracle Reports enables you to display data such as total number of pages or grand totals, in the report margins or on the report header pages. This option, although useful, forces the entire report to be "fetched ahead". Fetching-ahead requires the entire report to be processed before the first page can be output. The usual model is to format pages as and when required.

Although the fetched-ahead functionality does not affect the overall time the report takes to generate, it affects the amount of temporary storage required and the time taken before the first page can be viewed. This is an example of perceived performance as opposed to actual performance. If the report is to be output to the screen in a production environment, fetching ahead should be avoided unless the performance variance is deemed acceptable.

24.6.2 Bursting and Distribution

With report bursting, a report layout can be made up of three distinct sections: header, body, and trailer. A report can comprise all three sections, or it can be viewed as three separate reports within one report. Oracle Reports enables you to control bursting at group record level offering a further level of granularity. This is made possible by the Distribution and Repeat On properties for each individual section. The performance gain is evident when bursting is used in conjunction with distribution, allowing each section of a report to have multiple formats and sent to multiple destinations. Once the distribution options has been set the report needs only to be run once, to be output to multiple destinations with a single execution of the query(s). Previously the report had to be executed multiple times.

When you implement bursting and distribution in a report, you can generate section-level distribution by setting the Repeat On property for a section to a data model break group, which generates an instance of the section for each column record of that break group. Then, you can distribute each instance of the section as appropriate (for example, to individual managers in the MANAGER group).

If you set the Repeat On property for more than one of the Header, Main, and Trailer sections of a report, all Repeat On property values must be set to the same data model break group. If the Repeat On property for any one of the Header, Main, and Trailer sections is set to a different data model break group, Oracle Reports raises any of the following messages:

REP-0069: Internal Error
REP-57054: In-Process job terminated: Terminated with error
REP-594: No report output generated