Abstract: Provided are a method, system, and program for mirroring data. A relationship is established between a plurality of source data units in a primary storage and a plurality of corresponding target data units in a secondary storage. An operation is initiated to perform an initial copy of all source data units in the relationship to the corresponding target data units. An update is received to a source data unit and a determination is made of whether a first write mode is indicated. The update is copied to the source data unit in the first write mode to the corresponding target data unit if the first copy write is indicated. Otherwise, the update is copied to the source data unit corresponding target data unit in a second write mode if the first write mode is not indicated.

Abstract: Provided are a method, system, and article of manufacture for copying storage. Copy operations are performed on source storage units to copy to target storage units, wherein the copy operations create a consistent copy of the source storage units in the target storage units. While performing a copy operation to copy from one source storage unit to one target storage unit, a write operation is restricted from being performed on the one source storage unit, until the copy operations have been performed on the source storage units.

Abstract: Provided are a method, system, and program for managing a relationship between one target volume and one source volume. For each of the source volume and target volume, the memory includes: (i) at least one element, wherein each element represents a range of sequential data units in the volume; (ii) at least one relationship entry, wherein each relationship entry represents one relationship; (iii) at least one element pointer associating one element with one relationship entry, wherein the data units represented by the element are part of the relationship represented by the relationship entry that the pointer associates with the element; and (iv) one relationship pointer for each relationship entry associating the relationship entry with volume metadata, wherein the volume metadata provides information on the relationship represented by the relationship entry.

Abstract: Provided are a method, system, and program for accessing a resource. Requests are generated to access a resource in a first access mode and a second access mode. The requests are processed to access the resource in the second mode before processing at least one request to access the resource in the first access mode. The processing of the requests to access the resource in the first access mode is delayed for a time period after processing all the requests to access the resource in the second access mode in order to wait to receive a subsequent request to access the resource in the second access mode.

Abstract: Provided are a method, system, and program for establishing a point-in-time copy. A source relationship data structure and target relationship data structure are generated when establishing a point-in-time copy relationship between source and target storage areas, wherein the source and target relationship data structures each include an indicator for each source storage area and corresponding target storage area in the point-in-time copy relationship. The source and target relationship data structures are initialized to set the indicator for each source storage area and corresponding target storage area in the point-in-time copy relationship to a first value. A determination is made that data was written to one target storage area after establishing the point-in-time copy relationship. The indicators in the source and target relationship data structures corresponding to the source storage area and corresponding target storage area to which data was written are set to a second value.

Abstract: Disclosed is a method, system, and program for reducing an mount of data transferred. Indicators of sub-blocks modified for a block of data since the block of data was last sent to remote storage are maintained until the block of data is demoted. The maintained indicators are used to identify sub-blocks on the block of data for transfer to the remote storage.

Abstract: Disclosed is a method, system, and program for determining which data to remove from storage. A first policy is used to determine when to remove a block of data of a first type. A second policy is used to determine when to remove a block of data of a second type.

Abstract: Disclosed is a system, method, and article of manufacture for maintaining consistent copies of data between a primary site and a secondary site.

Abstract: Disclosed is a system, method, and article of manufacture for maintaining data integrity. A frequency for creating consistent transactions sets is negotiated. A consistent transactions set creation duration is negotiated. At an interval determined by the frequency, during the consistent transactions set creation duration, processing of a first consistent transactions set is completed, while processing of a second consistent transactions set is delayed until the end of the consistent transactions set creation duration. After the first consistent transactions set have been offloaded to secondary storage, consistent copies of data may be created.

Abstract: Provided are a method, system, and program for providing a mirror copy of data. An update to a primary storage is received and transferred to an intermediate system in a first transfer mode. The update is transferred from the intermediate system to a secondary storage in a second transfer mode, wherein the secondary storage provides a mirror copy of updates to the primary storage.

Abstract: In a system including a host, a primary storage subsystem coupled to the host, a cache coupled to the host and separate from the primary storage system, a secondary storage subsystem, and a data mover coupling the primary and secondary storage systems, data is temporarily cached for future storage in the primary storage subsystem so as to preserve timestamp information and maintain data consistency for asynchronously mirroring the data at a secondary subsystem.

Abstract: A method for sending a message from one host (16) to at least one other host, both of which are attached to a hardware subsystem (12) that is bidirectionally coupled to a mass data storage unit (14) includes (a) transferring a Send Message command through a channel (18) from a first attached host to the hardware subsystem, the Send Message command having at least one second attached host as an intended recipient; (b) buffering (20) at least a message payload portion of the Send Message command at the hardware subsystem and generating an unsolicited interrupt in the at least one second attached host; and (c) in response to the unsolicited interrupt, transferring a Request Message command through a channel from the at least one second attached host to the hardware subsystem for obtaining at least the message payload portion buffered at the hardware subsystem.

Abstract: A method and system for updating status information in a persistent storage. The method comprises the steps of defining a table in persistent storage (NVS) for holding information about changes to the status information; and when that status information is changed, making an entry in the table to record the changed information. A task is initialized to update the information on the disk drive. This updating is done by (i) checking the table to determine if any changes have been recorded in the persistent storage, and (ii) if any changes have been recorded in the persistent storage, then copying the status information from the persistent storage to the disk drive.

Abstract: A method for assuring consistency between a primary volume and a remote secondary volume wherein a host CPU manages track-to-track transfers using loosely-coupled, storage control unit mediated, data paths. The method includes initial volume synchronization in which concurrent updates to primary tracks are serialized by the copy progression at the secondary volume according to address. The method further includes volume resynchronization in the event of extrinsic error, fault, or the like in which the status of primary tracks updated during a volume suspension interval utilize bit maps to determine status of tracks unmodified during the suspension interval, and updated tracks and timestamps in addition to addresses. The bit maps and timestamps preserve the most recent version copy order of the tracks on the secondary volume.

Abstract: Disclosed is a method, system, program, and data structures for maintaining electronic data at a point-in-time. A first data structure indicates point-in-time data at one of a first storage location and a corresponding second storage location. A second data structure indicates point-in-time data at one of a first storage location and corresponding second storage location. A first relationship data structure indicates a relationship between the first storage location and corresponding second storage location and a second relationship data structure indicates a relationship between the first storage location and second storage location. A request to process the first storage location is processed by processing the first relationship data structure to determine the corresponding second storage location for the first storage location and processing the first data structure to determine whether data at the first storage location was transferred to the second storage location.

Abstract: There is provided a method, system and program storage device for asynchronously transmitting one or more incremental database updates from a primary volume at a primary site to a remote volume at a remote site, the primary site and the remote site interconnected by at least one communication link, the method, system and program storage device comprising: destaging modified data to the primary volume for a current database update and updating one or more bits in a first bitmap at the primary site that indicate one or more tracks on the primary volume that are to be overwritten with the modified data; transferring the first bitmap to a second bitmap at the primary site for indicating the modified data that is to be transmitted to the remote volume at the remote site for the current database update; and synchronizing the primary volume at the primary site with the remote volume at the remote site for the current database update by transmitting the modified data to the remote volume as indicated by one or more b

Abstract: Provided is a method, system, and program for releasing storage space in a first and second storage devices. Updates to the first storage device are copied to the second storage device to provide secondary storage for the updates. A first and second tables map data sets to addresses in the first and second storage devices, respectively. A first command is detected to invalidate data sets in the first table. The addresses in the first table comprise virtual addresses, and a third table provides a mapping of the virtual addresses to physical storage locations in the first storage device. A second command is generated to update the second table to invalidate the data sets in the second storage device invalidated in the first table by the first command. A third command is detected to invalidate the virtual addresses in the third table used by the data sets invalidated in the first table to free the physical storage locations in the first storage device pointed to by the invalidated virtual addresses.

Abstract: A method for assuring consistency between a primary volume and a remote secondary volume wherein a host CPU manages track-to-track transfers using loosely-coupled, storage control unit mediated data paths. The method includes initial volume synchronization in which concurrent updates to primary tracks are serialized by the copy progression at the secondary volume according to address. The method further includes volume resynchronization in the event of extrinsic error, fault, or the like in which bit maps and timestamps are used to determine the status of primary tracks either lost while in flight to the secondary volume or updated during a volume suspension interval. The bit maps and timestamps preserve the most recent version copy order of the tracks on the secondary volume.

Abstract: Disclosed is a method, system, program, and memory for erasing data. A request to erase data at least one storage location is received. In response, a data structure is generated indicating that each storage location subject to the erase request is in an erased state. Upon processing a request to access a storage location, a determination is made as to whether the requested storage location is indicated in the data structure. The data structure is processed to determine whether the requested storage location is in the erased state after determining that the requested storage location is indicated in the data structure. Access to the data at the requested storage location is denied after determining that the requested storage location is in the erased state.

Abstract: In an expeditious approach to transmitting updated data objects from one computing site to another, a transmitting site compares an updated data object with its previous version, and only includes the changed subparts in its transmission to the receiving site. The data object is therefore sent in a compacted state. The transmitting site also sends a map showing the changed subparts's relative positions within the entire data object. The receiving site retrieves a locally stored previous version of the data object, and combines the data object's unchanged subparts with the changed subparts recently sent by the transmitting site.