Tailoring for Performance › Fine Tuning

Fine Tuning

In tuning the performance of your application, consider these recommendations:

• Restrict the use of subfile control selectors to essential fields, especially on large files. Drop those that are not required. This applies to SELRCD, DSPFIL, and EDTFIL functions.
• Minimize the use of virtual fields. That is, use access paths with the least virtuals possible, since using them involves more processing. Where possible, direct processing to read one file instead of join logicals over multiple files. If appropriate, use the Retrieve Object (RTVOBJ) function instead.
• Consider the amount of Refers to referential checking:
  • Drop unused relations using the Edit Format Relations panel in the device design editor
  • Set relations to user checking where a field is required but referential checking is not
• Drop fields from panel formats if the application does not need them, rather than hiding the fields.
• If you need to validate many files, consider the use of Share Open Data Path when an access path is used frequently by several successive programs with fully restricted key access.
• Create native objects; that is, model value YCRTENV is set to QCMD (iSeries creation environment).

There are also closely related aspects to tailoring access paths.

For more information on tailoring access paths, see Building Access Paths in the chapter "Tailoring for Performance."