How To Convert From Rollback To Undo

BACKGROUND & OVERVIEW

This document provides a step-by-step guide to switching from manual rollback segments to automatic undo segments.

STEP-BY-STEP GUIDE

  • Shutdown the database.
  • Comment out, or remove, the rollback segments from the init.ora file. e.g.
      # rollback_segments = 'rbs01','rbs02',...
  • Start the database - this will force the SYSTEM rollback segment to be used.
  • Drop the rollback segment tablespace, including data files and rollback segments. e.g.
     DROP TABLESPACE rbs INCLUDING CONTENTS AND DATAFILES
     /
  • To maintain the cosmetics of the file system, and where possible, the file system name should be changed from rbs to undo. e.g.
      mv /u04/oradata/SID/rbs /u04/oradata/SID/undo
  • Create the undo tablespace. e.g.
      CREATE UNDO TABLESPACE <tablespace name>
      DATAFILE '<file specification>'
      SIZE <tablespace size>
      EXTENT MANAGEMENT LOCAL AUTOALLOCATE 
      /
  • Shutdown the database.
  • Update the init.ora file with the undo parameters. e.g.
     undo_management = auto
     undo_tablespace = <tablespace name>
  • Start the database.
  • The database will now be using automatic undo segments.
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