Browse Prior Art Database

Minimize Data Loss After a Data File Error

IP.com Disclosure Number: IPCOM000119406D
Original Publication Date: 1991-Jan-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 1 page(s) / 47K

Publishing Venue

IBM

Related People

Elliott, LC: AUTHOR [+4]

Abstract

Disclosed is an algorithm which provides for some level of database consistency, after an unrecoverable I/O failure. This algorithm allows for the recovery of the database to run to completion and indicates which file(s) have the I/O failure(s).

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 75% of the total text.

Minimize Data Loss After a Data File Error

      Disclosed is an algorithm which provides for some level of
database consistency, after an unrecoverable I/O failure. This
algorithm allows for the recovery of the database to run to
completion and indicates which file(s) have the I/O failure(s).

      The user can query the database and use the database as long as
the file with the I/O failure is not needed. Utilities can be
constructed which could possibly extract and reconstruct the data
from the file with the I/O failures.  Also, the user might be able to
construct the lost file via other means.  At any rate, this technique
minimizes the need for the user to restore the entire database after
an unrecoverable I/O failure.

      IF AN ERROR IS DETECTED ON A DATABASE FILE, THEN ALL THE
INTERNAL BUFFER POOL BUFFERS FOR THE FILE ARE WRITTEN TO DISK AND THE
BUFFERS are purged from the buffer pool.  After all the buffers are
purged, the file is renamed to a file which has the same primary
name, but with an error extension.  If there is already an error file
with that new name, then the original file is copied over the already
existing error file.

      Whenever an attempt to access the old file is detected, by the
existence of the renamed file, a "renamed error" is returned.  This
"RENAMED ERROR" IS REMEMBERED BY THE SYSTEM, BUT IS TREATED AS IF IT
WERE A SUCCESSFUL STATUS VIA THE SYSTEM RESTART CODE.

      When system restart completes, if the "renam...