PMDF uses an option file to provide a means of overriding the default values of various parameters that apply to PMDF as a whole. Various PMDF channels also have their own channel-level option files. This (global) PMDF option file has the same format but is otherwise distinct --- it applies to PMDF as a whole and not to any specific channel.
A variety of configuration options are controlled by options in the PMDF option file. In particular, the option file is used to establish sizes of the various tables into which the configuration and alias files are read.