Abstract: Provided are a method, system, and article of manufacture, where a plurality of extents are stored in a first set of storage units coupled to a controller. A determination is made that a second set of storage units has been coupled to the controller. The plurality of extents are distributed among all storage units included in the first set of storage units and the second set of storage units.

Abstract: Provided are a method, system, and article of manufacture, where a plurality of extents are stored in a first set of storage units coupled to a controller. A determination is made that a second set of storage units has been coupled to the controller. The plurality of extents are distributed among all storage units included in the first set of storage units and the second set of storage units.

Abstract: Provided are a method, system, and article of manufacture for managing write requests in cache directed to different storage groups. A determination is made of a high and low thresholds for a plurality of storage groups configured in a storage, wherein the high and low thresholds for one storage group indicate a high and low percentage of a cache that may be used to store write requests to the storage group. A determination is made of a number of tasks to assign to the storage groups based on the determined high and low thresholds for the storage groups, wherein each task assigned to one storage group destages write requests from the cache to the storage group.

Abstract: Provided are a method, system, and article of manufacture for using different algorithms to destage different types of data from cache. A first destaging algorithm is used to destage a first type of data to a storage for a first duration. A second destaging algorithm is used to destage a second type of data to the storage for a second duration.

Abstract: Provided are a method, system and program for using multiple data structures to manage data in cache. A plurality of data structures each have entries identifying data from a first computer readable medium added to a second computer readable medium. A request is received for data in the first computer readable medium. A determination is made as to whether there is an entry for the requested data in one of the data structures. The requested data is retrieved from the first computer readable medium to store in the second computer readable medium in response to determining that there is no entry for the requested data in one of the data structures. One of the data structures is selected in response to determining that there is no entry for the requested data in one of the data structures and an entry for the retrieved data is added to the selected data structure.

Abstract: Provided are a method, system, and program for managing data. A scan request is received to remove data from cache included in a relationship after the relationship is established. Processing the scan request is delayed for a delay time in response to receiving the scan request. After the delay time, a determination is made as to whether a condition with respect to the scan request is satisfied. The scan request is processed to remove data from cache that is included in the relationship associated with the scan request if the condition is satisfied.

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: 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: In a first form, a method for managing requests in a disk array having a number of disks includes associating priorities with respective requests. A new request is processed, which includes determining a maximum priority for at least certain ones of requests received and comparing the priority of the new request to the maximum priority. Responsive to the comparison, a selection is made between i) categorizing the new request as a foreground disk operation and ii) categorizing the new request as a background disk operation. A selection is also made between i) working the new request on at least one of the disks and ii) placing the new request in a queue.

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 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 system for enhancing the efficiency of communication between one or more host computers and a storage system controller during a data search within either the associated storage systems or within the storage system controller itself. A storage system controller, coupled to one or more host computers via multiple communication channels, is utilized to control access to one or more direct access storage devices. A host computer authorizes the storage system controller to search within a range of data locations within the storage system, sets an initial location from which the data search will begin, and specifies a key field argument to search for. The host computer then permits the storage system controller to independently search the authorized range of data locations within the storage system or within cache memory within the storage system controller.

Abstract: In a data storage system having a direct access storage device (DASD) and a cache, a cache directory has two types of directory entries. A track directory entry TDE identifies up to one DASD track of data records currently stored in cache. All records stored in a DASD track can be stored in a cache storage space allocated for the DASD track identified by the TDE. A cylinder directory entry CDE identifies a number N of records from any track in a respective cylinder of tracks. N is a positive integer less than the total number of records storable in a DASD track. From one to all of the DASD tracks in one cylinder may be identified in a CDE. The cache data storage allocation corresponding to a CDE is the same as that allocated for a TDE. Each TDE is addressed by a DASD track address of a cylinder while a CDE is addressed using a pseudo track number corresponding to a servo track in the DASD. A record cast out control for the cache includes examining the number of records destaged.

Abstract: The invention teaches a system and method for temporarily buffering data written to a storage system by a host computer. The storage system includes direct access storage devices and a cache. The cache is used as the buffer for both caching and noncaching data records before destaging to a direct access storage device. Upon receipt of a channel program from a host computer containing data for records to be updated, the storage controller determines if the records are currently cached. If the records are not cached, a write miss has occurred. Upon a write miss the storage controller checks an attribute transmitted in the channel program to determine if the records have a regular format. Records having a known, regular format are buffered in cache until destaged by a background process.