To handle RM/COBOL indexed data files, you map a file to IDXFORMAT=21 in the File Handler configuration file.
Within the configuration file, you can apply IDXFORMAT 21 to all files in a particular folder, all files with a specific file extension, or a single file. See Format of the Configuration File for the tags that you can use for the mapping, and the order in which settings in these tags are applied.
The order that the mapping is applied is important, as conflicting settings can be overwritten; for example, the following excerpt of the configuration file sets all files in usr/files/rmfiles to IDXFORMAT 21 and all files with a .DAT extension to IDXFORMAT 17:
[FOLDER:usr/files/rmfiles] IDXFORMAT=21 [*.DAT] IDXFORMAT=17
If there is a .DAT file in usr/files/rmfiles, the mappings are applied according to the type of tag. In the case above, mappings in the extension tag are applied after mappings in the FOLDER tag, and so the .DAT file in that directory has an IDXFORMAT of 17.
By default, the File Handler handles all sequential and relative data files, but if you want to handle them through the RM/COBOL file handler, use the INTEROP=RM configuration option; however, in cases where the INTEROP and IDXFORMAT mappings conflict, the INTEROP setting will override IDXFORMAT for your RM/COBOL indexed data files.