Abstract: An apparatus, system, and method are disclosed for continuously protecting data. A mirror module mirrors a primary record set to a base record set. A log module accumulates each record change to the primary record set in a log. A change selection module selects a record change from the log. A change application module applies the selected record change to the base record set to form a recovered record set.

Abstract: A method, apparatus and program storage device for providing asynchronous status messaging in a data storage system Asynchronous events are returned from a target to an initiator in response to a Read Message from the initiator. The return status message may or may not be associated with a previously given command or Logical Unit (LUN).

Abstract: A method is disclosed to write data to an information storage and retrieval system comprising (n) volumes and a data cache, where that information storage and retrieval system is capable of communicating with one or more host computers. The method receives from a host computer an update for the (i)th volume, and determines the (i)th delay, where that (i)th delay is associated with the (i)th volume. The method then writes the update to said data cache interposing the (i)th delay without indicating to said host computer that the information storage and retrieval system is unavailable.

Abstract: A method of recovery from a data storage system failure in a data storage system having a host computer writing data to a first storage unit with a first storage controller synchronously mirroring the data to a second storage unit, and with a second storage controller asynchronously mirroring the data to a third storage unit. Upon detection of an error or failure associated with the first storage unit, the synchronous data mirroring relationship between the first storage unit and the second storage unit is terminated and the host is directed to write data updates directly to the second storage unit. Upon correction of the failure associated the asynchronous mirroring of data updates from the second storage unit to the third storage unit is suspended and synchronous mirroring of the data updates in a reverse direction, from the second storage unit to the first storage unit, is commenced.

Abstract: A method, apparatus and program storage device for providing asynchronous status messaging in a data storage system Asynchronous events are returned from a target to an initiator in response to a Read Message from the initiator. The return status message may or may not be associated with a previously given command or Logical Unit (LUN).

Abstract: A method to copy information to two data storage devices. The method provides a first data storage device and a second data storage device, where the first data storage device is capable of communicating with the second data storage device. The method provides first information and a write command to the first data storage device at a first time. The method determines if the write command comprises a synchronous copy attribute. If the write command comprises a synchronous copy attribute, then the method synchronously provides the first information to the second data storage device. Alternatively, if the write command does not comprise a synchronous copy attribute, then the method provides the first information to the second data storage device at a second time, where that second time is later than the first time.

Abstract: A method of recovery from a data storage system failure in a data storage system having a host computer writing data to a first storage unit with a first storage controller synchronously mirroring the data to a second storage unit, and with a second storage controller asynchronously mirroring the data to a third storage unit. The method begins with the detection of a failure associated with the first storage unit. Upon detection of the error or failure associated with the first storage unit, the synchronous data mirroring relationship between the first storage unit and the second storage unit is terminated and the host is directed to write data updates directly to the second storage unit. Upon correction of the failure associated with the first storage unit, the asynchronous mirroring of data updates from the second storage unit to the third storage unit is suspended and synchronous mirroring of the data updates in a reverse direction, from the second storage unit to the first storage unit, is commenced.

Abstract: A method to initialize information disposed in an information storage and retrieval system comprising a data cache and one or more information storage media comprising a plurality of addresses. The method receives an initialization command, where that initialization command comprises a range of addresses and, optionally, an initialization pattern, where the plurality of addresses includes the range of addresses. The method forms and saves state information, where that state information includes the initialization pattern, and generates and saves a plurality of indicators, where that plurality of indicators includes an indicator for each track comprising the range of addresses. The method sets each of those indicators to a first value thereby indicating special handling, and provides an ending status signal, such that the receiving step, forming step, generating step, setting step, and providing step are performed substantially synchronously.

Abstract: A method, apparatus and program storage device for providing asynchronous status messaging in a data storage system Asynchronous events are returned from a target to an initiator in response to a Read Message from the initiator. The return status message may or may not be associated with a previously given command or Logical Unit (LUN).

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: A method and apparatus for improving storage controller throughput and reducing unit control block contention when selecting a Utility Volume for servicing non-specific read requests. Throughput is increased by enabling the storage controller to service non-specific read requests issued against a Utility Volume which is not the same as the device associated with the data that the non-specific read is requesting. The Utility Volume is dynamically selected by considering the current loads on the available devices for both specific and non-specific processing. A Penalty Index is assigned to each volume, wherein the Penalty Index is a weighted average of the specific and non-specific processing. The device having the lowest Penalty Index is selected as the Utility Volume for a session. A Penalty Index evaluation is made at a Reference Point which is further enabled by a random clock to ensure that sessions do not likely pick the same Utility Volume.

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 remote copy system incorporates dynamically modifiable ports on the storage controllers such that those ports can operate either as a control unit link-level facility or as a channel link-level facility. When configured as a channel link-level facility, a primary storage controller can appear as a host processor to a secondary storage controller. Using dynamic switches coupled between primary and secondary sites, fewer ESCON communication links are required since the ESCON communication links can function either as a channel or as storage controller communication link.

Abstract: A method and system are disclosed for transferring backup copies of designated multi-track datasets which are stored in a plurality of storage subsystems to a host system via data channel during concurrent execution of an application. Upon receiving a request for a backup copy, execution of an application is temporarily suspended. A dataset logical-to-physical storage system address concordance is formed and execution of the application is resumed thereafter. Any application initiated updates to affected tracks within the designated datasets which occur prior to generation of a backup copy are processed by buffering the updates, copying the affected tracks to storage subsystem memory, updating the address concordance and writing the updates to the affected tracks within the dataset.

Abstract: A method and apparatus for improving storage controller throughput when servicing non-specific read requests. Throughput is increased by enabling the storage controller to service non-specific read requests issued against a device address which is not the same as the device address associated with the data that the non-specific read is requesting. The device address associated with the data is thus free to be used for another I/O operation. When the device address used by the non-specific read is a non-busy type (that is, the device and/or data is not locked) then the throughput improvement is obtained by increasing the number of data requests that may be concurrently handled by the storage controller.

Abstract: A mechanism for controlling the powering-on and powering-off of control units in a data processing system having a plurality of channels, a plurality of control units, and a communications network of links for linking the channels to the control units. Each control unit includes a power-control table for recording power-control allegiance of the control unit to the channels. Where a control unit receives a power-on command from a channel, it records the identity of the channel in its power-control table. When a channel orders a control unit to power-off, the control unit checks to see if it owes power-control allegiance to the ordering channel. If it does, the control unit deletes the identity from its power-control table. The control unit will not power-off unless its power-control table is empty, indicating that it does not owe allegiance to any other channel.

Abstract: A data backup copying session on a data processing system is secured responsive to initiation of the data backup session by an application executing on a processing unit by generating a unique identifier for the data backup session. Thereafter, all member paths of a group of paths designated by the processing unit for communication between itself and the first storage subsystem are identified and associated with the data backup session. Access to the session is thereafter allowed only along a member path of the group of paths associated with the data backup session. The system and method of the invention further provide for fault recovery and protection against excessive demand on storage control unit memory.

Abstract: A method and system for efficiently accessing desired datasets among multiple datasets which are stored at specific data addresses within multiple storage subsystems which are coupled to a host system via a storage subsystem controller and a data channel. A data request is transmitted from the host system to the storage subsystems via the data channel. The data request specifies non-address attributes for desired datasets, such as boundary addresses for large data extents including many datasets or a request for all datasets modified since the occurrence of a specified event. The data request is then processed at the storage subsystem controller to determine a data address for each dataset within the storage subsystem which possess the desired attributes. Thereafter, the desired datasets are transmitted via the data channel to the host system in association with a specific address for each dataset.