Browse Prior Art Database

Count Key Data Architecture Data Attribute Detection

IP.com Disclosure Number: IPCOM000103952D
Original Publication Date: 1993-Feb-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Eggenberger, JS: AUTHOR

Abstract

The invention disclosed is a protocol which prevents potential data loss and preserves data integrity on count key data direct access storage device (DASD) architecture when a failure to detect both the sync byte and data attributes occurs.

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This is the abbreviated version, containing approximately 56% of the total text.

Count Key Data Architecture Data Attribute Detection

      The invention disclosed is a protocol which prevents potential
data loss and preserves data integrity on count key data direct
access storage device (DASD) architecture when a failure to detect
both the sync byte and data attributes occurs.

      Subsystems using DASD devices with count key data (CKD) or
extended count key data (ECKD) architectures have no knowledge of the
number of records on a track.  The data records in this type of
architecture are each preceded by a sync byte, followed by data
attribute bits.  The data attribute bits serve as a back-up indicator
that data will follow, in case the sync byte is missed due to errors.

      Subsystems will continue to read data until a sync byte and/or
data attribute patterns are no longer detected.  A problem arises
when an error causes both the sync byte and the subsequent cell
containing the data attributes.  When this type of error occurs, the
subsystem erroneously assumes that there is no more data to be read.
The proposed protocol prevents this data loss exposure.

      The invention is applicable for both 2,7 and 1,7 channel
encoding.  A 2,7 encoding scheme requires that data be encoded such
that no less than two, but no more than seven ZEROES occur between
ONE's in a data stream.  This information is written to the disk.
Areas where no data is written contain repeating "PAD" data in the
form "1000100010001..."  A 1,7 encoding schem...