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Technique for Data Recovery Excluding Portions of the Log without Requiring a Full Image Copy

IP.com Disclosure Number: IPCOM000106503D
Original Publication Date: 1993-Nov-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Goldsmith, J: AUTHOR [+2]

Abstract

A technique for Point-in-time recovery records the relative byte address(RBA) of the database log to which the object is restored. Subsequent recovery, whether to currency or point-in-time, utilize the recorded RBA(s) to navigate the log. Navigation through the log is achieved without user intervention. The resultant data is in a valid state.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 56% of the total text.

Technique for Data Recovery Excluding Portions of the Log without Requiring a Full Image Copy

      A technique for Point-in-time recovery records the relative
byte address(RBA) of the database log to which the object is
restored.  Subsequent recovery, whether to currency or point-in-time,
utilize the recorded RBA(s) to navigate the log.  Navigation through
the log is achieved without user intervention.  The resultant data is
in a valid state.

Technical Description - Several database structures and facilities
are utilized for this invention:

1.  Logging - Databases keep a 'journal' of activity against the
    data.  This 'journal' is called a log.  The DB2 log has a common
    referencing technique based on position, called relative byte
    address (RBA).

2.  Image Copy - Image copies are backup copies of data taken from
    the database object at specified points in time recorded as RBAs.

    Image copies are used as a base to restore data for the user
    should a hardware or logical data error occur.

3.  Database Catalog - The database catalog stores system information
    about the definition and processing in the database.  For DB2,
    the germane object to this invention is SYSIBM.SYSCOPY which
    records the image copy activity and recovery historical
    information.

      RECOVER is a DB2 utility that restores data to an operable
condition.  RECOVER analyzes the DB2 catalog to determine which image
copy and log (i...