Abstract: Providing snapshots for a logical device includes maintaining a global sequence number for the logical device, providing a snapshot table having a plurality of entries, where each of the entries corresponds to a targetless snapshot and includes a sequence number associated with a particular one of the targetless snapshots, the sequence number corresponding to the global sequence number at a time each of the snapshots is created, and, if a sequence number associated with a specific portion of the logical device is less than the global sequence number, then prior to moving new data to a specific portion of the logical device, copying old data from the specific portion to a location in a pool device, setting a pointer in a replication data pointer table to point to the location in the pool device and setting the sequence number associated with the specific portion to equal the global sequence number.

Abstract: Establishing a plurality of storage areas includes associating each of a first plurality of storage areas of a first type that contain sections of data with corresponding ones of second plurality of storage areas of a second type having pointers to alternative sections of data storage areas of the first type, where initially none of the second plurality of storage areas is available for accessing data corresponding thereto, and, after associating all of the first and second plurality of storage areas, activating the second plurality of storage areas to make the second plurality of storage areas available for accessing data. Exclusive access may be enabled for all of the first plurality of storage areas prior to activating the second plurality of storage areas or to each storage area one at a time.

Abstract: A method for copying data from a source logical device to a destination logical device. In response to a copy command from a requesting host application identifying the source and destination logical devices, an environment is established. Thereafter a calling system receives an immediate response that the copy operation is complete even though no data has been copied. Application programs may access storage locations in either the source or the destination logical device during the copy phase. A copy program transfers the date on a track-by-track basis to the destination logical device. Procedures assure that any data access to a particular track in either the source or destination logical device by any application prior to the transfer of that track is accommodated to maintain data integrity.

Abstract: Ordering data writes include a host computer providing a plurality of data writes to a primary storage device, the primary storage device assigning a first sequence number to data writes begun after a first time and before a second time, the primary storage device assigning a second sequence number, different from the first sequence number, to data writes begun after the second time, in response to completion of all writes assigned the first sequence number, the primary storage device transferring writes assigned the first sequence number to a secondary storage device, and, in response to the primary storage device transferring all writes assigned the first sequence number to the secondary storage device, the primary storage device sending a commit message to the secondary storage device. Ordering data writes may also include, in response to receiving a commit message from the primary storage device, the secondary storage device storing the data writes having the first sequence number.

Abstract: Using a local storage device to read desired data stored on a remote storage device that receives chunks of data from the local storage device includes, if the desired data is entirely in a cache of the local storage device, the local storage device returning the data from the cache and, if the desired data is not entirely in a cache of the local storage device, reading data from the remote storage device to the local storage device and the local storage device merging the data from the remote storage device with data from the local storage device at the local storage device. Using a local storage device to read desired data stored on a remote storage device that receives chunks of data from the local storage device may also include, prior to reading data from the remote storage device to the local storage device, creating a temporary storage area at the local storage device if there is data from the local storage device that is to be read. The temporary storage area may be a scratch slot.

Abstract: Accessing stored data includes providing a virtual storage area having a table of pointers that point to one of: a disk storage area and a volatile memory area, wherein the virtual storage area contains no sections of data, in response to a request for accessing data of the virtual storage area, determining whether a corresponding one of the pointers points to the disk storage area or points to the volatile storage area and accessing the data from the disk storage area or from the volatile storage area. Accessing stored data may also include associating a first one of the other storage areas with the virtual storage area, wherein the virtual storage area represents a copy of data of the disk storage area. Accessing stored data may also include causing all of the pointers of the table to initially point to sections of the disk storage area when the virtual storage area is initially associated with the disk storage area.

Abstract: Accessing stored data includes providing a virtual storage area having a table of pointers that point to sections of at least two other storage areas, where the virtual storage area contains no sections of data, in response to a request for accessing data of the virtual storage area, determining which particular one of the other storage areas contain the data, and accessing the data on the particular one of the other storage areas using the table of pointers. Accessing stored data may also include associating a first one of the other storage areas with the virtual storage area, where the virtual area device represents a copy of data of the first one of the other storage areas. Accessing stored data may also include causing all of the pointers of the table to initially point to sections of the first one of the other storage areas when the virtual storage area is initially associated with the first one of the other storage areas. The storage areas may be storage devices. The sections may be tracks.

Abstract: Accessing stored data includes providing a virtual storage area having a table of pointers that point to sections of at least two other storage areas, where the virtual storage area contains no sections of data, in response to a request for accessing data of the virtual storage area, determining which particular one of the other storage areas contain the data, and accessing the data on the particular one of the other storage areas using the table of pointers. Accessing stored data may also include associating a first one of the other storage areas with the virtual storage area, where the virtual area device represents a copy of data of the first one of the other storage areas. Accessing stored data may also include causing all of the pointers of the table to initially point to sections of the first one of the other storage areas when the virtual storage area is initially associated with the first one of the other storage areas. The storage areas may be storage devices. The sections may be tracks.

Abstract: Handling data includes providing a first storage area of a first type that contains sections of data, providing a second storage area of the first type that contains sections of data, providing a third storage area of a second type where the second type has, for each section thereof, a pointer to one of: a corresponding section of data of the first storage area and a corresponding section of data of the second storage area, causing the third storage area to be not available for accessing, and after causing the third storage area to not be available for accessing, providing data from the second storage area corresponding to pointers of the third storage area that point to sections of the second storage area.

Abstract: Restoring data includes providing data in a first storage area that contains sections of data, providing data in a second storage area where the second type has, for each section of data thereof, at least one of: a pointer to a corresponding section of data of the first storage area and a pointer to corresponding section of data of a third storage area of the first type. In one embodiment, a sections of the first storage area are replaced with pointers to the third storage area. In other embodiments, sections of a fourth storage area of the first type are replaced with pointers to the third storage area and optionally with pointers to the first storage area. In another embodiment, data is copied from the second storage area to a third storage area of the second type.

Abstract: Accessing data includes a host establishing a relationship between a first storage area of a first type containing data and a second storage area of a second type containing pointers to data provided in storage areas of the first type, where the storage areas are provided in a storage device coupled to the host. In response to the host writing data to a particular section of the first storage area after establishing the relationship, the particular section is copied from the first storage area to a third storage area of the first type prior to the write operation being executed. A corresponding pointer of the second storage area is adjusted to point to the third storage area.

Abstract: Ordering data writes include a host computer providing a plurality of data writes to a primary storage device, the primary storage device assigning a first sequence number to data writes begun after a first time and before a second time, the primary storage device assigning a second sequence number, different from the first sequence number, to data writes begun after the second time, in response to completion of all writes assigned the first sequence number, the primary storage device transferring writes assigned the first sequence number to a secondary storage device, and, in response to the primary storage device transferring all writes assigned the first sequence number to the secondary storage device, the primary storage device sending a commit message to the secondary storage device. Ordering data writes may also include, in response to receiving a commit message from the primary storage device, the secondary storage device storing the data writes having the first sequence number.

Abstract: Ordering data writes include a host computer providing a plurality of data writes to a primary storage device, the primary storage device assigning a first sequence number to data writes begun after a first time and before a second time, the primary storage device assigning a second sequence number, different from the first sequence number, to data writes begun after the second time, in response to completion of all writes assigned the first sequence number, the primary storage device transferring writes assigned the first sequence number to a secondary storage device, and, in response to the primary storage device transferring all writes assigned the first sequence number to the secondary storage device, the primary storage device sending a commit message to the secondary storage device. Ordering data writes may also include, in response to receiving a commit message from the primary storage device, the secondary storage device storing the data writes having the first sequence number.

Abstract: Accessing stored data includes providing a virtual storage area having a table of pointers that point to one of: a disk storage area and a volatile memory area, wherein the virtual storage area contains no sections of data, in response to a request for accessing data of the virtual storage area, determining whether a corresponding one of the pointers points to the disk storage area or points to the volatile storage area and accessing the data from the disk storage area or from the volatile storage area. Accessing stored data may also include associating a first one of the other storage areas with the virtual storage area, wherein the virtual storage area represents a copy of data of the disk storage area. Accessing stored data may also include causing all of the pointers of the table to initially point to sections of the disk storage area when the virtual storage area is initially associated with the disk storage area.

Abstract: Accessing stored data includes providing a virtual storage area having a table of pointers that point to one of: a disk storage area and a volatile memory area, wherein the virtual storage area contains no sections of data, in response to a request for accessing data of the virtual storage area, determining whether a corresponding one of the pointers points to the disk storage area or points to the volatile storage area and accessing the data from the disk storage area or from the volatile storage area. Accessing stored data may also include associating a first one of the other storage areas with the virtual storage area, wherein the virtual storage area represents a copy of data of the disk storage area. Accessing stored data may also include causing all of the pointers of the table to initially point to sections of the disk storage area when the virtual storage area is initially associated with the disk storage area.

Abstract: A method for copying data from a source disk storage device to a destination disk storage device. In response to a copy command from a requesting host application identifying the storage locations in source and destination disk storage devices, an environment is established. Thereafter a calling system receives an immediate response that the copy operation is complete even though no data has been copied. Application programs may access storage locations in either the source or the destination disk storage device during the copy phase. A copy program transfers the date on a track-by-track basis to the storage locations in the destination disk storage device. Procedures assure that any data access to a particular track in either the source or destination disk storage devices by any application prior to the transfer of that track are accommodated to maintain data integrity.

Abstract: Ordering data writes include a host computer providing a plurality of data writes to a primary storage device, the primary storage device assigning a first sequence number to data writes begun after a first time and before a second time, the primary storage device assigning a second sequence number, different from the first sequence number, to data writes begun after the second time, in response to completion of all writes assigned the first sequence number, the primary storage device transferring writes assigned the first sequence number to a secondary storage device, and, in response to the primary storage device transferring all writes assigned the first sequence number to the secondary storage device, the primary storage device sending a commit message to the secondary storage device. Ordering data writes may also include, in response to receiving a commit message from the primary storage device, the secondary storage device storing the data writes having the first sequence number.

Abstract: Reading desired data from a remote storage device that receives chunks of data from an other storage device includes determining if the desired data is part of a chunk of data committed by the other storage device, if the desired data is not part of a chunk of data committed by the other storage device, reading the desired data from a corresponding standard logical device, and if the desired data is part of a chunk of data committed by the other storage device, transferring the desired data to the standard logical device and obtaining the desired data from one of: the standard logical device after transferring the desired data thereto and the chunk of data committed by the other storage device. Reading desired data from a remote storage device may also include, if the desired data is part of a chunk of data committed by the other storage device, locking a corresponding slot of a cache only virtual device that points to the desired data.

Abstract: A method for copying a data file from a source device to a destination device. In response to a copy command from a requesting host application identifying the source file and the storage locations in a destination, an extents track is formed to establish an environment in which the file will be copied. The calling system receives an immediate response that the copy operation is complete even though no data has been copied. Application programs may access the file in either the source or the destination. A copy program transfers the file on a track-by-track basis to the destination storage locations. Procedures assure that any data access to a particular track in either the source or destination by any application prior to the transfer of that track are accommodated to maintain data integrity.

Abstract: Ordering data writes include a host computer providing a plurality of data writes to a primary storage device, the primary storage device assigning a first sequence number to data writes begun after a first time and before a second time, the primary storage device assigning a second sequence number, different from the first sequence number, to data writes begun after the second time, in response to completion of all writes assigned the first sequence number, the primary storage device transferring writes assigned the first sequence number to a secondary storage device, and, in response to the primary storage device transferring all writes assigned the first sequence number to the secondary storage device, the primary storage device sending a commit message to the secondary storage device. Ordering data writes may also include, in response to receiving a commit message from the primary storage device, the secondary storage device storing the data writes having the first sequence number.