Abstract: A host processor(s) is loosely-coupled by a plurality of data channels to a peripheral subsystem(s). The host processor(s) has a time of day clock. The peripheral subsystem(s) has a cluster(s) that performs peripheral controller functions. Each cluster has first and second clocks that respectively generate a log entry (logging) reference time and a subsystem time. The first and second clock times result in subsystem time stamps in a log that are not related to the time of day clock. For time correlating the time of day clock with the first and second clocks, a host time stamp is generated from the time of day clock. The host time stamp is sent to the subsystem via one of the data channels for entry into the log with the current time stamps of the first and second clocks as a time-correlating entry.

Abstract: 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.