International Business Machines Corporation

Joseph Smith Hyde

Brent Cameron Beardsley

Susan Kay Candelaria

Michael T Benhase

Thomas Charles Jarvis

Michael Howard Hartung

Robert Louis Morton

Lawrence Carter Blount

Vernon John Legvold

John Norbert McCauley

Douglas A Martin

Joel H Cord

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.

Method and system for staging data into cache

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. The storage system controller examines multiple records within the authorized range of data locations to locate a desired record associated with the key field argument and presents a status report to the host computer only after the desired record is located or the entire range of data is searched and the desired record was not located. Allowing the storage system controller to independently search records and report status only after completion of an attempt to find a desired record within an authorized range of records minimizes communication overhead. Reducing the number of status reports presented over the communication channel enhances communication efficiency.

Method and system for data search in a data processing system

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. Based on the number of records cast out from cache to DASD, a cache event parameter CEP is modified or maintained. Accessing cache requires examining a current CEP value for each accessed DASD track to access either the TDE or CDE.

Accessing cached data in a peripheral disk data storage system using a

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.

Method and system of buffering data written to direct access storage

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Tucson, AZ, United States of America

Joseph Smith Hyde