HP 3000 Manuals HP 3000 Manuals
Influencing Performance What Your System Can Do For Performance [REV BEG] Proper system configuration can have an important impact on all database and I/O on your system. Consult your system reference manuals for information about system configuration.[REV END] Datasets and files spread over several disks can improve performance of a report when it accesses multiple datasets or files at the same time, which is when you use keyed access. What HP ALLBASE/BRW Can Do For Performance With HP ALLBASE/BRW you can tune a report's data access for best execution performance without changing the relational data access definition. This means that the report always prints the same data, regardless of the sequence in which the datasets or files are accessed, which keys are used and whether serial access is used. See Chapter 3, "Understanding Relational Data and Tables," and Chapter 6, "Defining Data Access," for more information about the relational data access definition. In addition to tuning single reports, you can improve overall performance of multiple reports by using the multi-pass reporting features described in Chapter 12, "Multi-Pass Reporting and Output Files." To find the optimal data access method for a single report, use the following description of how HP ALLBASE/BRW performs data access and the hints about data access methods and when to use them. Access Blocks A report is executed in one or more phases, called access blocks. Each access block inputs data, processes and optionally sorts it, and then outputs the data. The last access block prints the report and creates the output files (if any). The previous access blocks create temporary work files used by other access blocks. Compiler Optimizations The HP ALLBASE/BRW compiler translates the relational access definition into the access blocks needed for the selected access methods. In addition, it optimizes the data access, so that: * data selections are performed as early as possible * table calculated items are calculated as early as possible * the number of items is reduced to only those used in the report The compiler generates a listing which shows how the relational access definition was translated and the optimizations which have been performed. This listing is discussed in more detail later in this chapter.