Browse Prior Art Database

Simple Data Integrity Method for Spanned, Segmented Data

IP.com Disclosure Number: IPCOM000108321D
Original Publication Date: 1992-May-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 79K

Publishing Venue

IBM

Related People

Gregg, LE: AUTHOR [+2]

Abstract

A technique to very simply detect a data integrity problem when data stored on an auxiliary storage device is read for further processing is disclosed.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Simple Data Integrity Method for Spanned, Segmented Data

       A technique to very simply detect a data integrity
problem when data stored on an auxiliary storage device is read for
further processing is disclosed.

      Many situations in data processing require modification to an
existing large collection of data.  At some point, this data
collection will probably be stored on a more permanent storage
device, such as magnetic disk.  Then, at some time in the future, the
data will again be read into main memory and used as is or even more
modifications may be made.

      The problem with this scenario is that, after the data is
modified, it may be only partially stored on the "permanent" storage.
A power failure or some other failure may interrupt the write
operation.  In the case of a power outage, there is no program or
error handling routine available to invoke to take corrective action;
the problem of the partially written data must be detected at the
next time the data is used.

      The following simple technique was developed to detect data
integrity problems of this type.  This technique requires no
additional direct access storage device (DASD) sectors and no
additional write operations before or after writing the main data
collection.

      The technique itself is very simple:  allocate two additional
data areas of perhaps 8 bits each within the data collection.  One
data area is at the beginning, and the second is at the end.
Actually, in most cases, a single bit in the first and last bytes
will suffice.  See the figure for a simple diagram of the data areas.

      These two new data areas are used to contain nothing more than
a count of the number of times the data area has been written to the
storage media.  Before th...