Abstract: A remote data shadowing system provides synchronous, storage based, real time disaster recovery wherein a secondary site is located remote from the primary site. An error recovery program at the primary site quiesces applications running thereat for performing error recovery procedures and signalling both primary and secondary locations that failed duplex has occurred. The error recovery program determines the cause of failed duplex, and if error recovery is successful, duplex mode is resumed. If the error recovery program is unable to perform error recovery successfully, then further write updates at the primary site are prohibited and an error message is communicated to operators at both the primary and secondary sites.

Abstract: A data copy validation technique compares primary data to a copy of that data by generating check codes of the data to be validated at both primary and secondary sites in a continuously running remote data shadowing system. The validation session runs concurrently with the data shadowing so as not to disrupt the data shadowing. Each data validation session is assigned a copy start time, for example, a time preceding a time of a consistency group, for defining when the check code for data at the primary should be compared to a check code of the data at the secondary. The check code of the data at the secondary site is taken at a time that is the equivalent logical point-in-time of that data at the primary site even though the respective data contents may be different in real time.

Abstract: A system for asynchronously duplexing direct access storage device (DASD) data in a plurality of DASD subsystems has the advantage of decoupling the data duplexing operation from the DASD write I/O operation. This ensures the write does not incur unnecessary wait states in the subsystem. By establishing a sequence checkpoint at which time a set of information packets are grouped together and processed as a single sequence unit, this decoupling and independent operation takes place. Through this independence, data copying to a secondary location can take place without affecting the performance of the subsystems and also not affecting the corresponding integrity of the data that is being updated.

Abstract: A method and system are disclosed for permitting high concurrency of access during backup copying of designated data stored within a storage subsystem which includes multiple storage devices coupled to the data processing system via a storage subsystem control unit having subsystem memory therein. Data within each storage device is accessed utilizing a Unique Control Block (UCB), which identifies a selected storage device, and an associated data retrieval command sequence which identifies the data to be accessed. Portions of the data copied to subsystem memory within the subsystem storage control unit as sidefiles from a first storage device may be accessed utilizing a Unique Control Block (UCB) associated with an alternate storage device by associating a selected data retrieval command sequence therewith which identifies the data as stored within the subsystem memory.

Abstract: A method in a data processing system for automatically terminating or resuming backup copy sessions after an abnormal interrupt or reset notification occurrence during a backup copy process. A status indication is entered into activity tables associated with a plurality of storage subsystems and devices within a data processing system in response to initiation of a backup copy session. Status indications are then entered upon successful completion of a backup copy session within the data processing system. The indications within the activity tables are reviewed to determine the status of a backup copy session upon restarting a resource manager, abnormal termination of a backup copy program, or an operating system initial program load. If a backup copy session has been initiated but not completed, the backup copy session is then terminated. The indications within the activity tables are also reviewed to determine the status of a backup copy session if a reset notification is raised by a storage subsystem.

Abstract: A method and system are disclosed for enhanced efficiency of backup copying of designated datasets stored within a plurality of storage devices coupled to the data processing system via a storage subsystem control unit having subsystem memory therein. Application execution within the data processing system is temporarily suspended long enough to form a dataset logical-to-physical system address concordance to be utilized to administer copying of the designated dataset. Thereafter, application initiated updates to uncopied portions of the designated datasets are temporarily deferred until sidefiles of the affected portions of the designated datasets are written to subsystem memory. The updates are then written to the storage subsystem. Portions of the designated datasets are then accessed and copied from the storage subsystem on a scheduled or opportunistic basis utilizing selected data retrieval command sequences.

Abstract: A method in a data processing system for generating a backup copy of designated datasets during concurrent execution of an application. Upon receiving a request for a backup copy, execution of an application is suspended. A dataset logical-to-physical storage system address concordance for the designated datasets is formed, and execution of the application is resumed thereafter. A resource manager is established to manage all input and output functions between storage subsystems, storage subsystem memory associated with each of the storage subsystems, and a temporary host memory during formation of the backup copy. Formation of the backup copy is accomplished on a scheduled or opportunistic basis by copying the designated datasets from the storage subsystems and then updating the address concordance in response to the copying.