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Browse Prior Art Database

Page Header for Database Files Which Provides for In-Place Expansion

IP.com Disclosure Number: IPCOM000119405D
Original Publication Date: 1991-Jan-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 1 page(s) / 41K

Publishing Venue

IBM

Related People

Elliott, LC: AUTHOR [+3]

Abstract

Disclosed is the format of a page header intended to provide for release to release in place conversion to an enhanced format via the maintenance of a pool of reserved space. This minimizes the probability of the user needing to run a backup/convert/restore utility when the software is upgraded.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 89% of the total text.

Page Header for Database Files Which Provides for In-Place Expansion

      Disclosed is the format of a page header intended to provide
for release to release in place conversion to an enhanced format via
the maintenance of a pool of reserved space. This minimizes the
probability of the user needing to run a backup/convert/restore
utility when the software is upgraded.

      The purpose for providing a pool of reserved space is in
anticipation of new (as yet undefined) requirements in the format of
the page.  For example, there may be new page header requirements or
new requirements for the data in the page.  Reserving this space
allows the new software to convert the page from the old format to
the new format when the data is first read in.  This "in-place"
format change avoids the need of special convert utilities which must
traverse the database and convert the files using a copy operation
during the convert.

      The format is defined as follows, where each page has the
standard header: ITEM    DESCRIPTION BEGOFF  Beginning offset (of the
data) in bytes DATLEN  Length of the data in Bytes REVNUM  Revision
number - identifies the format

      The BEGOFF identifies where the page data (non-header)
information begins.  The DATLEN represents the number of bytes
available or used for the data.  By making the BEGOFF longer than the
header, the unused space can be reserved for future expansion.  That
is, the new space can be used by changing the...