Abstract: A method and system for controlling data flow in a storage subsystem containing multiple cache and/or multiple NVS elements based on the operability of the cache arrays and NVS arrays. In a data processing system having a storage controller connecting a plurality of host processors and a plurality of storage devices, this invention provides a method and architecture for managing multiple storage elements within the controller, without a degradation in subsystem performance and without data integrity problems. A set of configuration registers is utilized by the microcontroller to direct cache and NVS access to the proper storage array. A configuration table is loaded with status information concerning the memory arrays at Initial Microcode Load(IML) and this information is periodically updated during controller operation.

Abstract: A storage system improves error debugging by directing distributed system components associated with an error condition to temporarily suspend data processing for collecting failure information. The collected failure information is correlated for later analysis according to an issued diagnostic state save channel command word (CCW) that is triggered by the detection of said error condition. The storage system includes a host processor running applications generating record updates. A data mover in the host processor issues the diagnostic state save CCW upon receiving an error code from one of the system components. The failure information includes software, hardware and microcode control structures of the distributed system components.

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: Often in DASD subsystems, circumstances can occur which prevent the full transfer of the required data from channel to subsystem during a write operation. The disclosed methods prevents this data from later being read and treated as valid data by the host processor. This is achieved by marking data as invalid within the storage subsystem once it is determined that a channel error has occured. Subsequently, upon reading that data, the host processor can be made aware of the data invalidity and treat the data accordingly. In a second embodiment, invalid data is discarded rather than stored over the previous valid version of the data, before it is ever stored on DASD.