Browse Prior Art Database

Track Promotion/Demotion to a Cache Store

IP.com Disclosure Number: IPCOM000100386D
Original Publication Date: 1990-Apr-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 1 page(s) / 57K

Publishing Venue

IBM

Related People

Benhase, MT: AUTHOR [+3]

Abstract

Control units containing a cache store can increase performance by satisfying the central processing unit requests for data by accessing cache store rather than accessing the direct access storage device (DASD). The overhead of promoting DASD data to the cache store can be minimized by not attempting to promote tracks with uncorrectable data checks in the fields that are not being referenced by the central processing unit, and by retaining tracks which contain data checks in the cache store longer to reduce the probability of needing to promote the track to the cache in the future.

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Track Promotion/Demotion to a Cache Store

       Control units containing a cache store can increase
performance by satisfying the central processing unit requests for
data by accessing cache store rather than accessing the direct access
storage device (DASD).  The overhead of promoting DASD data to the
cache store can be minimized by not attempting to promote tracks with
uncorrectable data checks in the fields that are not being referenced
by the central processing unit, and by retaining tracks which contain
data checks in the cache store longer to reduce the probability of
needing to promote the track to the cache in the future.

      The track promotion/demotion algorithm is sensitive to errors
in the transfer of data to and from the cache store. Transfer
continues if a correctable data check occurs. Transfer is aborted if
an uncorrectable data check occurs in a field that is not being
referenced by the channel and continues if the field is referenced by
the channel.  Tracks with uncorrectable data checks in fields not
referenced by the host are not transferred to the cache store.  The
cache store retains the tracks with the data checks longer to reduce
the time needed to potentially re-request the track. To limit the
amount of processing time consumed to promote any given DASD track to
the cache, the following rules are practiced.
      1.  Track promotion continues if a correctable data check
occurs.
      2.  Track promotion is aborted if an u...