Abstract: A volume-to-volume copy method on a DASD storage subsystem concurrent with host CPU application execution and referencing of data on a primary. In this method, updates to data made on a primary volume after the element was copied during a first pass will be deferred and copied only during a second pass rather than interrupting the first pass. This accumulation and deferral of updates to a second pass shortens the volume copy time and reduces application referencing delay.

Abstract: A data processing system executes a plurality of processes in parallel. The processes access shared user records stored in memory serially. One or more data structures are used to track access by processes to the data structures and to the user records. Responsive to a fault occurring in a first parallel process, a signal is given the remaining parallel processes indicating the failure. Responsive to the failure, it is determined if the faulting parallel process had access to one of the data structures. Depending upon the circumstances of access, integrity of the user records may be assumed and the record validated. The data structures themselves can be examined to determine if the contents of memory is reliable. Typically the data structures support use of the memory as a cache.