Browse Prior Art Database

Dynamic Adjustment of Open Data Files (Elastic Files)

IP.com Disclosure Number: IPCOM000109345D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Berman, E: AUTHOR [+3]

Abstract

A method for dynamically expanding or truncating a file while it is open is disclosed. A file being written can be either expanded or truncated to the desired size when the file is closed.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 87% of the total text.

Dynamic Adjustment of Open Data Files (Elastic Files)

       A method for dynamically expanding or truncating a file
while it is open is disclosed.  A file being written can be either
expanded or truncated to the desired size when the file is closed.

      The application program can provide the file system with the
record length and number of records at close time.  The file system
then does not have to audit the user every time it writes a block and
the user can have the file system automatically create a structurally
correct file for the user.

      Benefits of this invention:
.    When a fixed format file is written, a file may be dynamically
extended without the program issuing extra writes.  If the program
wants the file to be longer than the number of blocks already
written, the file system will calculate where the last record will be
and logically store sparse blocks to fill out the file.
.    When a fixed format file is written, a file may be dynamically
truncated to make it shorter than the number of blocks written.  If
the program had written too much data, it can close the file and tell
the file system to delete records from the end of the file.
Currently, there is no way for a program to do this without closing
and then reopening the file.
.    When a variable record length file is written, the program will
be able to delete records from the end of the file when the file is
closed.  The program will not be able to extend the file (t...