Browse Prior Art Database

Inverted ECC to Flag Unreliable Data

IP.com Disclosure Number: IPCOM000051173D
Original Publication Date: 1982-Aug-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Schmitt, SA: AUTHOR

Abstract

A disk attachment may use inverted check fields to flag unreliable data on an associated file. Unreliable data is generated by the data recovery procedures used during alternate sector assignment programs. Alternate sector assignment is done when it becomes impossible to use a given sector on the disk surface due to such things as grown surface defects.

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Inverted ECC to Flag Unreliable Data

A disk attachment may use inverted check fields to flag unreliable data on an associated file. Unreliable data is generated by the data recovery procedures used during alternate sector assignment programs. Alternate sector assignment is done when it becomes impossible to use a given sector on the disk surface due to such things as grown surface defects.

When it has been determined that it is no longer possible to write and read data in a given sector, the sector is flagged as defective and the data is moved to a new, alternate sector. Because the old sector was defective, the data recovered from it and moved to the alternate sector may have been incorrect and traditionally has been flagged as unreliable. This flag has been a flag bit in the identifier field.

The unreliable data flag bit in the identifier field is undesirable because it makes the error recovery more complicated. Any read or write command issued to the sector will fail with a no record found error because of the flag bit. During the recovery for the no record found error, the program must sort out the real problem and take appropriate action.

By using an inverted check field on the unreliable data for the flag, the error recovery is less complicated. During a write operation, the data field and check field are rewritten. This automatically removes the bad data indicator with no error recovery or lost time.

During a read operation a data check is generated by the inverted check field. This will cause the system to attempt error correction. Because the inverted check fi...