Browse Prior Art Database

Partial Track Staging

IP.com Disclosure Number: IPCOM000045321D
Original Publication Date: 1983-Mar-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Duke, AH: AUTHOR [+4]

Abstract

A DASD (direct-access storage device) is coupled to a host via a cache memory. It is desired to have complete copies of tracks in cache that are to be accessed by the host for improving performance in a track that is accessed by the host at a point other than within a given distance from an index or reference point, then that track is partially staged to the cache beginning at the point of first reference R1 and continuing through the index point, i.e., the latter portion of the track. If the reference to the track is within a given percent of the total data stored on the track, then the entire track is promoted to cache.

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Partial Track Staging

A DASD (direct-access storage device) is coupled to a host via a cache memory. It is desired to have complete copies of tracks in cache that are to be accessed by the host for improving performance in a track that is accessed by the host at a point other than within a given distance from an index or reference point, then that track is partially staged to the cache beginning at the point of first reference R1 and continuing through the index point, i.e., the latter portion of the track. If the reference to the track is within a given percent of the total data stored on the track, then the entire track is promoted to cache. Otherwise, only a part of the DASD track is promoted to cache; that portion of the track on DASD not promoted to cache can be promoted later upon a later reference to such data or upon any one of a plurality of staging criteria which may include intent signals received from the host as to the characteristics of desired data transfers.

The host requests data from the peripheral storage system including the cache. A directory for the cache is searched to determine whether or not space has been allocated in the cache for the upcoming data transfer. If such space has been allocated, then the data access is made to the cache without reference to the DASD. In the event that data space is not allocated in the cache, a so- called cache miss occurs, requiring the accessing of the DASD. Such accessing can result in transferring data from DASD to cache. It is desired to keep allocated space in the cache to the track granularity. Accordingly, it is desired to promote a complete track to cache whenever possible. However, promoting a complete track of data to cache results in extra data no...