DOVEX tells SCHED to write a VEX format output file. VEX is the format used by PCFS, the NASA/Goddard field system that controls EVN, geodetic and other stations. It will also be used by MkIV correlators (under construction). A VEX file is only required if a station controlled by PCFS is included or if the observation is to be processed on a correlator that requires a VEX file. Pure VLBA or VLBA plus other stations that use VLBA control files (VLA, EB_VLBA, GB_VLBA) do not require a VEX file.
If any station in the schedule requires a VEX file, as specified in the CONTROL input in the station catalog, DOVEX will be set automatically. The only occasions in which DOVEX will need to be specified by the user are those when an observation with no VEX stations is to be correlated at a VEX driven correlator. This is likely to be rare. Note that SCHED should not be used to prepare observations that are to be correlated at a MkIII correlator (e.g. Bonn), because it doesn't produce the proper Mark III ``.drg file''.