Browse Prior Art Database

Method to Improve the Headswitch Access Time of Direct Access Storage Device (DASD) Files

IP.com Disclosure Number: IPCOM000122751D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 73K

Publishing Venue

IBM

Related People

Erickson, KJ: AUTHOR [+2]

Abstract

A method is described that can be used to reduce the overall headswitch access time in direct access storage device (DASD) files that especially improves on the overall read or write operation time for large data transfers involving data on more than one data track. This method provides a means to effectively minimize any misalignment that exists between the data tracks in each cylinder, thereby requiring less compensation action for the correction of any misalignment when accessing data on successive tracks.

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Method to Improve the Headswitch Access Time of Direct Access Storage
Device (DASD) Files

      A method is described that can be used to reduce the overall
headswitch access time in direct access storage device (DASD) files
that especially improves on the overall read or write operation time
for large data transfers involving data on more than one data track.
This method provides a means to effectively minimize any misalignment
that exists between the data tracks in each cylinder, thereby
requiring less compensation action for the correction of any
misalignment when accessing data on successive tracks.

      The main cause for significant headswitch times in DASD devices
is due to misalignment of the inactive read/write heads with their
associated data tracks while the active read/write head is aligned
with its associated data track. During a headswitch operation any
misalignment that exists on the track being switched to must be
compensated for by repositioning the read/write head for that track,
which can take a substantial amount of time depending on the degree
of misalignment.

      The procedures being used today for the storage of data DASD
devices employ a format whereby data is stored on successive tracks
of a cylinder as each track becomes fully utilized.  Therefore, as
data is either stored or retrieved from the device, a number of
headswitch operations may occur to access data on the successive
tracks.  For each of these headswitch operations the...