Browse Prior Art Database

File Access Staging Facility for Computer Systems

IP.com Disclosure Number: IPCOM000108443D
Original Publication Date: 1992-Jun-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 3 page(s) / 145K

Publishing Venue

IBM

Related People

Eilbott, SA: AUTHOR

Abstract

Described is a software file access staging facility for computer systems that allows on-line programs to contend for the use of removable media by optimizing data accessibility. The facility allows on-line programs to contend for use of the removable media and to provide staging to occur external to the application.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 46% of the total text.

File Access Staging Facility for Computer Systems

       Described is a software file access staging facility for
computer systems that allows on-line programs to contend for the use
of removable media by optimizing data accessibility. The facility
allows on-line programs to contend for use of the removable media and
to provide staging to occur external to the application.

      Typically, accessing files found on removable media, such as
diskettes, tape, or optical discs, is relatively slow and only a
limited set of files may be mounted at any time as compared to files
recorded on fixed media. Occasionally, access requires the removable
media to either be mounted for long durations or mounted and
dismounted repetitively.  If a file is left mounted, then the drive
on which the volume is mounted is monopolized.

      The concept described herein provides access via DASD to files
normally resident on the removable media.  The requesting software or
application specifies, by means of a staging process, when access to
the file is about to start and when access to the file is no longer
required.  This staging process provides for the mounting of the
removable volumes and manages the use of the DASD staging area.  Once
it is no longer required, if a file has been updated, the removable
volume is once again mounted and the file is updated thereon.  The
facility also has allowances for recovery after abnormal termination.

      The use of staging is specifically designed to overcome
performance penalties inherent in the direct access of files on
removable volumes.  Staging eliminates the need to keep a removable
medium mounted and the drive occupied with that volume for the entire
time that files on that volume are being accessed.  Staging the files
of interest frees the device to allow access to files on other
volumes; therefore, staging allows objects from many volumes to be
simultaneously available.  Once a file has been staged, it may
continue to be manipulated regardless of the status of the original
volume.

      Staging encompasses the use of a fixed medium, such as a DASD
drive, as a temporary repository for files on the removable media and
to allow multiple requests for the same file to access the temporary
copy simultaneously.  This repository for the temporary copies is
called the staging area.

      Several major operations are involved in the staging function:
      -    Immediate Stage File - This operation, initiated by a
requester, requests immediate real-time access to a file managed by
the file manager.  If there is already a copy of this file in the
staging area, a pointer to that file is returned to the requester.
If the file is not already in the staging area and the file resides
on a removable volume, the volume will be mounted, the file will be
copied to the staging area, and the volume will be dismounted.  If
read/ write access to the file is requested, another copy of the
file...