Is it possible you mean the Domesday Book, otherwise known at the great survey? As far as I know it was the only inventory mandated by William the Conqueror and it was at his Christmas court at Gloucester in 1085 where William decided he wanted a survey of all the lands in England, all livestock, who held what, and what taxes were due. It was completed in 1086 and included most of England and much of Wales.
The Millinium File is a database created by the Institute of Family Research but you'd have to ask them why it is so named. It is basically one of several compendium databases which blend information from a variety of sources. It's not a substitute for researching your own family history and at best is a basic starting point. But without verification you can't consider any such information to be accurate. It just gives you a general idea of where to look. Jay