Browse Prior Art Database

Data Migration and Recovery with Non-Readable Tracks

IP.com Disclosure Number: IPCOM000113906D
Original Publication Date: 1994-Oct-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 84K

Publishing Venue

IBM

Related People

Beardsley, BC: AUTHOR [+5]

Abstract

Data migration between DASD devices is often done to capture data from a failing device before the device becomes unusable. The data on the failing device may have portions of the recording surface that are damaged or unreadable by the time the migration is initiated. To avoid aborting the migration when an unreadable track is encountered, the track will be flagged on the device to which data is being migrated to prevent access of that track until it is initialized and allow the migration to continue. In addition, any data pinned in cache for the failing device will be copied from cache to the migration device. Description - Data migration between DASD devices is necessary when DASD devices will be removed and replaced by newer models.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 51% of the total text.

Data Migration and Recovery with Non-Readable Tracks

      Data migration between DASD devices is often done to capture
data from a failing device before the device becomes unusable.  The
data on the failing device may have portions of the recording surface
that are damaged or unreadable by the time the migration is
initiated.  To avoid aborting the migration when an unreadable track
is encountered, the track will be flagged on the device to which data
is being migrated to prevent access of that track until it is
initialized and allow the migration to continue.  In addition, any
data pinned in cache for the failing device will be copied from cache
to the migration device.  Description - Data migration between DASD
devices is necessary when DASD devices will be removed and replaced
by newer models.  Migration between DASD is also done before
servicing devices to allow for continuous access to the data.  That
is, while data is being moved from a device needing service action to
a free volume, reads and writes of the data are allowed.  After the
migration is complete the original source volume can be serviced.

      Because of physical imperfections to a recording surface,
physical damage to a recording surface, or because magnetic recording
material will tend to fade over time, certain regions of the DASD may
not be readable at the time the migration is done.  Currently, when
data migration mechanisms encounter a track that cannot be read from
the source device, the migration aborts with an error code informing
the user of the unreadable track.  To continue the migration, the
unreadable track must be repaired or its location reassigned.  The
migration must then be restarted, usually from the beginning of the
volume.  This procedure is done for each track individually.  A
migration will not be successful until full readability has been
restored to all tracks of the source volume.  Even unused tracks must
be repaired before a migration is possible.  If pinned data exists in
the control unit, the recovery is even more complicated.  Currently
migration cannot take place until the pinned data is discarded.
Discarding data requires...