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Blind Head Scrub Error Recovery Procedure for Magnetic Tape Subsystem

IP.com Disclosure Number: IPCOM000109397D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 80K

Publishing Venue

IBM

Related People

Greco, MB: AUTHOR [+3]

Abstract

The problems addressed by this article are: 1. The decoupling of tape repositioning for repetitive movement across a tape cleaner blade from the data blocks already on tape. 2. Structuring tape cleaner blade motion to be programmable with variable distance and frequency parameters. 3. Utilizing tape cleaner blade motion to aid in recovering from read as well as write error scenarios.

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Blind Head Scrub Error Recovery Procedure for Magnetic Tape Subsystem

       The problems addressed by this article are:
1.   The decoupling of tape repositioning for repetitive movement
across a tape cleaner blade from the data blocks already on tape.
2.   Structuring tape cleaner blade motion to be programmable with
variable distance and frequency parameters.
3.   Utilizing tape cleaner blade motion to aid in recovering from
read as well as write error scenarios.

      In the process of reading data from magnetic media, debris can
collect along the tape path and adhere to either the tape or the
Read/ Write Magnetic Recording (MR) Head.  Typically, there is a Tape
Cleaner Blade (TCB) attached to the MR head which is responsible for
scraping the tape clean before it passes under the read detection
circuitry.  The single pass, however, can be insufficient.  Debris
can interfere with the read signals in such a way as to make the
encoded data undecipherable.  Traditional error recovery upon
encountering a bad block is to move tape back a sufficient number of
blocks to again achieve a pass across the Tape Cleaner Blade.  Yet,
block detection in the neighborhood of debris is often difficult and
using recorded data to reposition carries a high risk.  Also, in
implementations utilizing serpentine recording and/or an asymmetric
tape cleaner blade, there may be an insufficient number of blocks
laid down in the desired direction to use for positioning.

      Because of these difficulties, a new Error Recovery Procedure
(ERP) called the Head Scrub ERP was designed for the 3490E subsystem.
It takes advantage of the automatic repositioning capabilities of the
drive and a...