Browse Prior Art Database

Detect Read/Write Failures Earlier-Avoid Permanent Read Errors

IP.com Disclosure Number: IPCOM000113820D
Original Publication Date: 1994-Oct-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Allen, V: AUTHOR [+2]

Abstract

An indirect method of preventing permanent read errors on 3480/3490 compatible tape drives is disclosed. When a tape drive has a problem that causes permanent write data errors, critical tape volume control information stored on the tape may become corrupted. An indirect read/write test is performed in an area that does not contain customer data. This allows a drive problem to be detected before the customer write process and prevents data from being over-written. Since the old data is not corrupted by being over-written by data in error, the tape is still usable and the operation can be retried on another tape drive.

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

Detect Read/Write Failures Earlier-Avoid Permanent Read Errors

      An indirect method of preventing permanent read errors on
3480/3490 compatible tape drives is disclosed.  When a tape drive has
a problem that causes permanent write data errors, critical tape
volume control information stored on the tape may become corrupted.
An indirect read/write test is performed in an area that does not
contain customer data.  This allows a drive problem to be detected
before the customer write process and prevents data from being
over-written.  Since the old data is not corrupted by being
over-written by data in error, the tape is still usable and the
operation can be retried on another tape drive.

      There is a class of errors (Write Data Checks and Write ID Mark
Checks) caused by debris or defective hardware that may occur during
the initial processing of a tape volume.  If these errors occur when
a critical volume control record (known as VOL1) is being re-written
by a host system, the previous critical volume control record is
rendered unreadable.  This makes the tape's volume identification
unrecognizable to system software and will cause a permanent read
error to be logged upon each subsequent read attempt.

      To prevent these problems, the tape drive's microcode is
changed to perform a very short read/write test in the region of tape
preceding actual customer data (known as the format ID or VOL ID
region).  The test is performed before the actual customer data is
written and indirectly verifies that the drive currently has the
capability to write and read data on a...