Browse Prior Art Database

Automatic Media Maintenance by the I/O Subsystem

IP.com Disclosure Number: IPCOM000115670D
Original Publication Date: 1995-Jun-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 97K

Publishing Venue

IBM

Related People

Escola, DR: AUTHOR [+4]

Abstract

Non-customer data tracks on the Head/Disk Assemblies (HDAs) in the IBM* 9340 subsystem are used to hold subsystem microcode, subsystem log information, subsystem status information, and alternate track location information. These non-customer data tracks are referred to as the Subsystem Support Tracks. When media problems are detected while accessing any data in the Subsystem Support Tracks, the subsystem will automatically invoke Media Maintenance. This novel function prevents the need to replace HDAs for media problems, since no customer applications can access these tracks due to the critical nature of the data which they contain. Since the alternate tracks are part of the Subsystem Support Tracks, Automatic Media Maintenance also includes the automatic reclamation of defective alternate tracks.

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Automatic Media Maintenance by the I/O Subsystem

      Non-customer data tracks on the Head/Disk Assemblies
(HDAs) in the IBM* 9340 subsystem are used to hold subsystem
microcode,
subsystem log information, subsystem status information, and
alternate track location information.  These non-customer data tracks
are referred to as the Subsystem Support Tracks.  When media problems
are detected while accessing any data in the Subsystem Support
Tracks, the subsystem will automatically invoke Media Maintenance.
This novel function prevents the need to replace HDAs for media
problems, since no customer applications can access these tracks due
to the critical nature of the data which they contain.  Since the
alternate tracks are part of the Subsystem Support Tracks, Automatic
Media Maintenance also includes the automatic reclamation of
defective alternate tracks.

      The Automatic Media Maintenance functions are a comprehensive
set of operations which enhance the capability of the subsystem by
ensuring Media Maintenance of the Subsystem Support Tracks can be
performed with no impact to the customer.  This set of functions also
manages the reclamation of alternate tracks, again in a manner
requiring no customer intervention.

      Three forms of Media Maintenance support exist in the IBM 9340
Direct Access Storage Subsystem.  These are maintenance of customer
data through the use of the Media Maintenance Assist orders and
sub-orders of the Perform Subsystem Function (PSF) command, Surface
Analysis Testing completed as part of the Manufacturing process, and
the Automatic Invocation of Media Maintenance of the Subsystem
Support Tracks.  This Technical Disclosure Bulletin describes the
Automatic Media Maintenance of the Subsystem Support Tracks.

      The Automatic Media Maintenance of the Subsystem Support Tracks
includes the following functions:
  1.  Automatic reclamation of defective alternates (all alternate
       tracks are part of the Subsystem Support Tracks), and
  2.  Automatic Media Maintenance of the remainder of the Subsystem
       Support Tracks.

Automatic Reclamation of Defective Alternates - When an alternate
track is found to be defective or contain an invalid assignment, the
Maintenance Control Facility (MCF) function of the 9340 microcode
will invoke the Device Management Facility (DMF) function of the
microcode to utilize the Media Maintenance command set to:
  1.  ...