Browse Prior Art Database

Interruptible Index Creation

IP.com Disclosure Number: IPCOM000121370D
Original Publication Date: 1991-Aug-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 1 page(s) / 50K

Publishing Venue

IBM

Related People

Comeau, A: AUTHOR [+2]

Abstract

Disclosed is a method to allow an index creation to be interrupted by a checkpoint. This method has been implemented in the SQL/DS relational database management system.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 58% of the total text.

Interruptible Index Creation

      Disclosed is a method to allow an index creation to be
interrupted by a checkpoint.  This method has been implemented in the
SQL/DS relational database management system.

      A checkpoint causes a snapshot of the database to be written to
non-volatile storage (DASD).  This copy of the database is the
starting point for recovery after a database failure.  The state of
the checkpointed database is completely described by those records
written to the log before the checkpoint record.  This requires that
all currently executing database operations complete and be logged
before the checkpoint is allowed to proceed.  Without this protocol,
a partially completed operation could be written to DASD, and there
would be no log record to denote the existence of this partial
change.

      Due to the long-running nature of index creation, a checkpoint
may be prevented from occurring for a substantial period of time.
During this time other users must wait, as their short-running
operations have already completed and they are simply waiting for the
checkpoint to occur.  The method described here avoids this database
unavailability by allowing a checkpoint to interrupt an index
creation.

      Index creation is now logged in two steps:
      1.   a log record is written just before the index
           creation begins.
      2.   another log record is written when the index
           creation co...