Browse Prior Art Database

Backup Table Token Linked List

IP.com Disclosure Number: IPCOM000104900D
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 70K

Publishing Venue

IBM

Related People

Bracht, CJ: AUTHOR [+3]

Abstract

Described is a method of determining which database objects to backup while running online.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 53% of the total text.

Backup Table Token Linked List

      Described is a method of determining which database objects to
backup while running online.

      The Backup Utility backs up database table objects (data,
index, and long field) page by page.  It uses common buffer pool
interfaces to read the pages of each object.

      The Utility also backs up non-table object files that are part
of the database such as the database configuration file, the log
control file, and the object relocation file (ORF).  The ORF contains
an entry for each table object contained in the database.  Each entry
defines the location of each of the object's files or parts.

      The Utility can execute online, that is, there can exist active
transactions against the database while it is being backed up.
However, the user must run Forward Recovery after restoring a
database backed up online to complete any partial transactions that
may have been backed up.

      Backup needs to backup the ORF prior to any table objects so
that it can be restored prior to restoring any table objects.  The
ORF is needed to know where to locate the table objects being
restored.

      Backup can determine what table objects exist at the start of
the backup by reading the rows from the system catalog,
SYSIBM.SYSTABLES.  However, the ORF and SYSTABLES may not be in sync.
New table objects can be created and/or old ones deleted in between
the time that the ORF is backed up and SYSTABLES is read.  This
causes the following problem during the restore process:

1.  The Backup Utility backs up the ORF.
2.  Then a new table object is created before or while Backup is
    reading the SYSTABLES catalog.  Rows are inserted into the new
    table object.
3.  Backup copies the new table object onto the Backup media.
4.  The user restores the database...