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: 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: 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: Provided is a method, system, and program for destaging data from a first computer readable medium to a second computer readable medium. A list of entries indicating data blocks in the first computer readable medium is scanned. For each entry scanned, a determination is made as to whether the data block indicated in the scanned entry satisfies a criteria. If the data block indicated in the scanned entry satisfies the criteria, then a destage operation is called to destage the data block in the scanned entry from the first computer readable medium to the second computer readable medium. If the called destage operation is not initiated, then the scanned entry is removed from the cache list. The removed scanned entry is added to one destage wait list. During one destage operation, data blocks indicated in entries in the destage wait list are destaged.

Abstract: A method and apparatus for improving write performance in a disk array, wherein unnecessary track grouping is avoided during writes, by using a full track write counter. When a write request is received, the full track write counter for tracks in a stripe of tracks associated with the write request is analyzed to determine whether the write request involves a full track write. A cache destage is subsequently executed based on the analysis. When the write to cache is a full track write, a previous track full track count is fetched from a previous track's full write counter, a full track count of the tracks associated with the write request are set to be equal to the minimum of either the stripe width or the previous track's full track count plus one.

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: In a cache management system multiple cache lists are utilized, where each entry in a list names at least one corresponding data item in cache. A cache manager always demotes cache list entries from a “current removal list” (and demotes or destages the corresponding data items from cache) until that list is exhausted and another list rotates into the function of current removal list. A prescribed order is established for rotating the role of current removal list. In response to prescribed activities of data items in cache, new cache list entries are added nearer or farther from the current removal list according to the prescribed order and the data items' priorities.

Abstract: In a cache management system multiple cache lists are utilized, where each entry in a list names at least one corresponding data item in cache. A cache manager always demotes cache list entries from a “current removal list” (and demotes or destages the corresponding data items from cache) until that list is exhausted and another list rotates into the function of current removal list. A prescribed order is established for rotating the role of current removal list. In response to prescribed activities of data items in cache, new cache list entries are added nearer or farther from the current removal list according to the prescribed order and the data items' priorities.

Abstract: Provided is a method, system, and program for destaging data from a first computer readable medium to a second computer readable medium. A list of entries indicating data blocks in the first computer readable medium is scanned. For each entry scanned, a determination is made as to whether the data block indicated in the scanned entry satisfies a criteria. If the data block indicated in the scanned entry satisfies the criteria, then a destage operation is called to destage the data block in the scanned entry from the first computer readable medium to the second computer readable medium. If the called destage operation is not initiated, then the scanned entry is removed from the cache list. The removed scanned entry is added to one destage wait list. During one destage operation, data blocks indicated in entries in the destage wait list are destaged.

Abstract: Disclosed is a method, system, and program for processing data access requests, such as read requests, to a storage location maintained in both a first storage, such as a cache, area and second storage area, such as a disk drive, during a destage operation. A destage operation is granted access to the storage location to destage data from the storage location in the first storage area to the second storage area. During the destage operation, a data access request is granted access to the storage location.

Abstract: Disclosed is a system for caching data. After determining a sequential access of a first memory area, such as a direct access storage device (DASD), a processing unit stages a group of data sets from the first memory area to a second memory, such as cache. The processing unit processes a data access request (DAR) for data sets in the first memory area that are included in the sequential access and reads the requested data sets from the second memory area. The processing unit determines trigger data set from a plurality of trigger data sets based on a trigger data set criteria. The processing unit then stages a next group of data sets from the first memory area to the second memory area in response to reading the determined trigger data set.

Abstract: A method and apparatus for improving write performance in a disk array is disclosed. The invention avoids unnecessary track grouping during writes by using a full track write counter. When a write request is received, the full track write counter for tracks in a stripe of tracks associated with the write request is analyzed, a determination of whether the write request involves a full track write is made and a cache destage is subsequently executed based on the analysis of the full track write counter for tracks in a stripe of tracks associated with the write request. The full track write counter is not incremented when the write to cache is not a full track write. When the write to cache is a full track write, a previous track full track count is fetched, a full track count of the tracks associated with the write request are set to be equal to the minimum of either the stripe width or the previous track's full track count plus 1.

Abstract: The present invention provides a monitoring system (30) for monitoring operation of dynamic plant apparatus (10, 100). Electronic processing means (31, 32, 33) is provided for processing the electrical parameter signals provided by sensors (11-15) and is capable of thereby producing a plurality of different fault signals. Display means (34) is provided for displaying fault information to a user of the monitoring system (30), the display means (34) being controlled by the fault signals produced by the electronic processing means (31, 32, 33). The electronic processing means (31, 32, 33) compares the values of at least some of the measured parameter signals with limit values stored in memory by the electronic processing means (31, 32, 33) and when the comparison shows that the value of a measured parameter signal is outside the respective limit value the electronic processing means (31, 32, 33) produces a respective basic fault token signal.

Abstract: A data processing system provides a method and apparatus for managing a shared resource between multiple processors. The data processing system includes a first processor for producing, or supplying, available sections of the shared resource, and a second processor for consuming, or allocating, the available sections within the system. The first and second processor share a memory containing a circular queue, a resource queue, for referencing available shared resource sections. The resource queue is initialized by storing a pointer to an available shared resource section in each entry of the resource queue. The second processor consumes an available section of shared resource by removing a resource pointer from a resource queue entry and sending a message signal to a mailbox message subsystem of the first processor.

Abstract: A mailbox message system is coupled between a processor having a mailbox and one or more peripheral devices or circuits communicating information to the processor. The mailbox message system in the present invention reports events which occur in the peripheral devices or circuits to the mailbox within the processor to be serviced by the processor. The mailbox message system receives inputs from the processor indicating which events are allowed to be currently serviced by the processor and stores these inputs in a first memory. The mailbox message system further receives unique signals representing distinct events from the peripheral devices and stores these signals in a second memory. The generated events which are pending service in the second memory are then compared with the allowed events in the first memory. When a match exists, a message is encoded and transmitted to the mailbox of the processor indicating that the processor has an event to be serviced.