File Definition Language (FDL) files define the attributes of RMS files. You can use FDL to specify RMS options and parameters that can be used when creating a file. If you use the callable FDL routines in a program, you can specify most RMS run-time options used when opening (or creating) a file and connecting a record stream. Although you can use FDL with sequential and relative RMS files, it is especially useful for defining RMS indexed files. Key definitions, area definitions, placement options, and bucket-size settings are typical of the information used to define indexed files that have optimal run-time performance. The following DCL commands invoke utilities that use FDL files: ANALYZE/RMS_FILE, CONVERT, CONVERT/RECLAIM, CREATE/FDL, EDIT/FDL Refer to the Guide to OpenVMS File Applications and the OpenVMS Record Management Utilities Reference Manual for information on FDL and the utilities that use FDL. See the OpenVMS Utility Routines Manual for information on the routines that use FDL files.