General tips about performance when you use File Manager functions

The following tips are provided as a guide to improving performance when using File Manager functions:

Use the FASTREXX subset of REXX

If a user PROC is required, it is strongly recommended that, rather than the full REXX language, the FASTREXX subset of REXX is used. File Manager provides a set of external REXX functions designed to allow many common tasks to be performed within the FASTREXX subset. See File Manager User’s Guide and Reference Chapter 14, "Enhancing File Manager processing" for a discussion of FASTREXX.

Template and copybook processing

The utilities DBX and DBI allow a copybook or template to be specified for the target/input data set, respectively. The utilities DBX, DBI, DBC, D2G, and DBP optionally require a Db2® template that describes the Db2® object to be processed. When using these functions, consider the following performance-related points:

• File Manager can be most efficient if a template is used instead of a copybook. If a copybook must be used, specify the language of the copybook. (LANG=COBOL, LANG=HLASM, or LANG=PLI, instead of the default LANG=AUTO) for best performance.
• Template expressions should be written, if at all possible, using expressions suitable for File Manager internal processing. For more details, see File Manager User’s Guide and Reference "Improving performance using internal expression processing".