Abstract: A digital data storage system comprising a mass storage subsystem in which information is stored on one or more disk storage units, with a storage element constituting a track on a disk storage device and each track storing a plurality of records. Each track in each disk storage device of the digital data storage system is associated with a descriptor. In that embodiment, when the control device retrieves the contents of a record, it can use the format definition type identifier of the descriptor associated with the track to determine the format definition type for the track, use the specific format information to determine the location and size of the record on the track, and retrieve the record.