There are several ways to create an RMSfile; the most common ways are with lfedit (C-1) or lfadmin (C-1). Lfedit interactively creates an RMS definition file; then creates the RMSfile from that definition. Lfadmin creates an RMSfile from an RMS definition file that you specify. Both lfedit and lfadmin add the new RMSfile to the catalog.
You can create an RMS definition file with the filedef (C-1) program.
Toolkit (C-1) invokes lfedit to create or modify RMSfiles.
Lfedit assumes that the RMSfile's pathname has the word data in it (e.g. data\mag or gl\data\ledger) and the pathname of the RMS definition file is the same as the RMSfile pathname with data replaced by def. The RMS definition files for the two previous examples would be def\mag and gl\def\ledger.