A detailed description of this function can be found in the report ALEPH 91-161 ( PHYSIC 91-137 ) .
The function XVDEOK returns .TRUE. if the VDET HV is on for the current event and .FALSE. otherwise. XVDEOK uses the HV bits and also calls KVGOOD (see below).
If you want to use tracks with high quality VDET data, first, check that the HV is on and second, check that the tracks in which you are interested have VDET hits (see QVDHIT above).
XVDEOK cannot work when one is reading a Nano-Dst.