Abstract: A target data storage system comprises a peer-to-peer communication link interface for linking the target to a source data storage system, and data storage for storing point in time copy data received from the source via the peer-to-peer communication link interface. Information is established at the target relating logical identification of the point in time copy data to point in time copy data stored at the target and to point in time copy data stored at the source, such that the information references the data storage system having requested point in time copy data. A controller of the target accesses requested point in time copy data at the target if the table indicates that the requested point in time copy data is available at the target; else obtains the requested point in time copy data from the source via the peer-to-peer communication link interface.

Abstract: For a technique for maintaining consistency of data, one or more blocks of data identified by a first structure are copied to form a consistent set of data. While not acknowledging completion of write requests to any blocks of data, a second structure is created, wherein the second structure indicates which blocks of data are modified while the consistent set of data is being formed.

Abstract: Provided are a method, system, and program for forming a consistency group of data. Information is provided on a consistency group relationship indicating a plurality of slave controllers and, for each indicated slave controller, a slave storage unit managed by the slave controller. A command is transmitted to each slave controller in the consistency group relationship to cause each slave controller to transmit data in the slave storage unit to a remote storage in a manner that forms the consistency group. A determination is made as to whether all the slave controllers successfully transmitted the data in the slave storage units that is part of the consistency group to the remote storage.

Abstract: Provided are a method, system, and program for managing data. A data request is received to a target track in a relationship, wherein the relationship associates a source track with the target track. A destage request to destage the source track is submitted in response to the data request to the target track, wherein executing the data request to the target track is conditioned on receiving a completion response to the destage request. If the source track is not in cache, then a complete response is returned to the destage request. If the source track was in cache when the relationship was established, then the destage request is added to an Input/Output (I/O) queue for the source track. After the source track is destaged in response to processing the destage request in the I/O queue, the complete response is returned to the destage request.

Abstract: A process, apparatus, and system for evaluating a projected cache size implement and manage one or more projected cache lists that each contains directory entries corresponding to a projected cache size. The projected cache size may be either smaller or larger than the actual size of a cache installed in a computer system. Using the projected cache list entries, performance statistics such as cache hit ratio and average access time are tracked for each list. The process, apparatus, and system may calculate performance parameters that describe the performance specific to the actual cache list and each projected cache list. The resulting performance statistics may be used to formulate an optimization parameter to be communicated to a user or an administrator application.

Abstract: Provided are a method, system, and program for establishing a point-in-time copy. Input/Output (I/O) requests to tracks identified as source tracks and corresponding target tracks in a point-in-time copy relationship are suspended until the point-in-time copy relationship is established. At least one data structure providing information on the source tracks and corresponding target tracks in the point-in-time copy relationship is generated, wherein the point-in-time copy relationship is established before data at the source tracks is copied to the target tracks and before source tracks in cache at the point-in-time are destaged to storage.

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 managing a relationship between one target volume and one source volume. Information is maintained in memory on an existing relationship between at least one source volume and at least one target volume, comprising: (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; and (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. A new relationship between at least one target volume and at least one source volume is added.

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: 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 technique for applying changes back to an original copy of data to reduce an amount of data transferred. A first indicator is maintained for each block of data in a first storage to indicate whether the block of data has been updated in the first storage since the block of data was last transferred to a second storage. A second indicator is maintained for each block of data in the second storage to indicate whether the block of data has been updated in the second storage since the block of data in the second storage was overwritten by a corresponding block of data in the first storage.

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. Disclosed is a method, system, and program for managing metadata in cache. A first policy is used to determine when to remove data from a primary cache, and a second policy is used to determine when to remove data from a metadata cache.

Abstract: Disclosed is a technique for reducing an amount of data transferred. A first indicator is maintained for each source block of data to indicate whether the source block of data has been updated in source storage since the source block of data was last transferred to target storage. A second indicator is maintained for each target block of data in target storage to indicate whether the target block of data has been updated in target storage since the target block of data was overwritten by a corresponding source block of data. When transferring data from the source storage to the target storage, each source block of data for which a first indicator has been set to indicate that the source block of data has been updated is transferred and each source block of data that corresponds to a target block of data for which a second indicator has been set to indicate that the target block of data has been updated is transferred.

Abstract: Provided are a method, system, and program for increasing processor utilization. A list of work is divided for processing among a plurality of processes, wherein a process is allocated a part of the list of work to process, and the processes execute in parallel. If a process completes the list of work allocated to the process then the process is made available on an available process queue. Before a process performs any work, the process reads the available process queue and determines if any process is available to share the work. If so, the work is split up between the examining process and the available process. In one implementation, the work involves scanning a cache and if necessary destage data.

Abstract: Provided are a method, system, and program for managing data. A data request is received to a target track in a relationship, wherein the relationship associates a source track with the target track. A destage request to destage the source track is submitted in response to the data request to the target track, wherein executing the data request to the target track is conditioned on receiving a completion response to the destage request. If the source track is not in cache, then a complete response is returned to the destage request. If the source track was in cache when the relationship was established, then the destage request is added to an Input/Output (I/O) queue for the source track. After the source track is destaged in response to processing the destage request in the I/O queue, the complete response is returned to the destage request.

Abstract: Provided are a method, system, and program for managing a relationship between one target volume and one source volume. Information is maintained in memory on an existing relationship between at least one source volume and at least one target volume, comprising: (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; and (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. A new relationship between at least one target volume and at least one source volume is added.

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: Disclosed is a technique for applying changes back to an original copy of data to reduce an amount of data transferred. A first indicator is maintained for each block of data in a first storage to indicate whether the block of data has been updated in the first storage since the block of data was last transferred to a second storage. A second indicator is maintained for each block of data in the second storage to indicate whether the block of data has been updated in the second storage since the block of data in the second storage was overwritten by a corresponding block of data in the first storage.

Abstract: Disclosed is a technique for reducing an amount of data transferred. A first indicator is maintained for each source block of data to indicate whether the source block of data has been updated in source storage since the source block of data was last transferred to target storage. A second indicator is maintained for each target block of data in target storage to indicate whether the target block of data has been updated in target storage since the target block of data was overwritten by a corresponding source block of data. When transferring data from the source storage to the target storage, each source block of data for which a first indicator has been set to indicate that the source block of data has been updated is transferred and each source block of data that corresponds to a target block of data for which a second indicator has been set to indicate that the target block of data has been updated is transferred.

Abstract: Provided are a method, system, and program for managing resources in which a local processor sends remote operation requests to be executed by a remote processor having multiple resources. In the illustrated embodiment, the local processor and the remote processor each have a resource manager, each of which maintains a control set for each resource of the remote processor. Each control set of the remote processor resource manager includes a queue for queuing remote operation requests awaiting execution in connection with the resource associated with the control set. Each control set of the local processor resource manager includes a credit counter which keeps track of permissible outstanding remote operation requests. Each local processor control set credit counter is decremented for each remote operation request for the associated resource sent to the remote processor and is incremented for each acknowledgment received from the remote processor.