Browse Prior Art Database

Non-sync Cache Track Image Error Recovery

IP.com Disclosure Number: IPCOM000121831D
Original Publication Date: 1991-Sep-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 1 page(s) / 58K

Publishing Venue

IBM

Related People

Leung, PL: AUTHOR [+2]

Abstract

In normal read/write operation, the device process will handle records consecutively as they are encountered on the DASD, either reading data from DASD to the Automatic Data Transfer (ADT) or writing data to DASD from the ADT. Situations exist where the device process must be able to reorient back to the beginning of a record being handled from the DASD. After reorientation is complete, any fields of the record already handled by the device process for a write operation are simply again written to the DASD by the device process. Any fields already marked valid for a read operation are clocked, or essentially spaced over without re-reading, by the device process to prevent unnecessary re-occurrences of any possible errors.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 62% of the total text.

Non-sync Cache Track Image Error Recovery

      In normal read/write operation, the device process will handle
records consecutively as they are encountered on the DASD, either
reading data from DASD to the Automatic Data Transfer (ADT) or
writing data to DASD from the ADT. Situations exist where the device
process must be able to reorient back to the beginning of a record
being handled from the DASD.  After reorientation is complete, any
fields of the record already handled by the device process for a
write operation are simply again written to the DASD by the device
process.  Any fields already marked valid for a read operation are
clocked, or essentially spaced over without re-reading, by the device
process to prevent unnecessary re-occurrences of any possible errors.

      To support caching operations, the device process will write
into electronic cache whatever data is currently being processed by
the DASD.  Whenever the device process reorients the DASD, it must
also perform an equivalent reorientation of the cache address pointer
to guarantee the integrity of the cache version of the data.

      The Synchronous read/write mode, in which the Channel and the
device process handle the same record at the same time, requires that
the error recovery process works in conjunction with the device
process when reorienting the cache image of the DASD record.  The
error recovery process corrects the cache image before DASD
reorientation.  The device process s...