PERIPHERAL SUBSYSTEM HAVING READ/WRITE CACHE WITH RECORD ACCESS

Data is accessed by record identification in a peripheral sub-system having cache and back store to transfer the most recently updated version of one or more records stored in the subsystem where one version of a record may be in a back store and a modified version of the record may be in a cache storage, by a method and apparatus including table lookup means for indicating for each record of each track of each device in said back store whether record data stored in cache is modified with respect to a version of the same record stored in back store; and means responsive to the indicating means for transferring the modified or backing store version of a record in accordance with predetermined criteria.