Automatic Undo Management

Automatic Undo Management (AUM) Submitted by admin on Wed, 2003-05-14 21:24 RDBMS Server In Oracle 8i and below, Rollback Segments provide read consistency and the ability to rollback transactions. In Oracle 9i, Undo segments can be used to provide this functionality. The advantage of using Automatic Undo Management is that it relieves the DBA of manually creating, sizing and monitoring the rollback segments in the database. To start using Automatic Undo Management one must create an UNDO- type tablespace and set some initialisation parameters. Create an Undo Tablespace: Oracle can only create undo segments in special UNDO-type tablespaces. One can create an undo tablespace with database creation or by creating separate UNDO tablespaces: -- Using the create undo tablespace statement CREATE UNDO TABLESPACE undots1 DATAFILE 'C:\Oracle\oradata\ORCL\orcl_undots101.dbf' SIZE 100M REUSE AUTOEXTEND ON; -- As part of database creation CREATE DATABASE orcl ... UNDO TABLESPACE undots2 DATAFILE 'C:\Oracle\oradata\ORCL\orcl_undots201.dbf' SIZE 100M AUTOEXTEND ON; Enable Undo Management: The following initialisation parameters can be used to enable and control AUM (do a "show parameters undo" to see your settings): UNDO_MANAGEMENT (MANUAL or AUTO) - One MUST set this parameter to AUTO to enable Automatic Undo Management. The default is MANUAL for both Oracle 8i and Oracle

Automatic Undo Management

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