My Oracle Support Banner

FAQ – Automatic Undo Management (AUM) / System Managed Undo (SMU) (Doc ID 461480.1)

Last updated on FEBRUARY 03, 2019

Applies to:

Oracle Database - Enterprise Edition - Version to [Release 9.0.1 to 18]
Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Backup Service - Version N/A and later
Information in this document applies to any platform.
Oracle RDBMS Server


This article is intended for Database Administrators with  knowledge on Automatic Undo Management (AUM).

Also covered major questions related to Automatic Undo Management (AUM) which will be helpful during creation (or) monitoring the undo tablespaces.

Questions and Answers

To view full details, sign in with your My Oracle Support account.

Don't have a My Oracle Support account? Click to get started!

In this Document
Questions and Answers
 What is Undo?
 Which are the major initialization parameters that controls AUM?

 How to set the undo_retention value ?
 What is the Fast Ramp-up Routine ?
How to switch to a new undo tablespace?
 What is UNDO Retention?
 What is Automatic UNDO Retention (10g New Feature)? Explain.
  Why TUNED_UNDORETENTION is calculated so high making undo space grow fast ?
 Explain the DBA_UNDO_EXTENTS View, and usage?
 What are the various statuses for Undo Extents? Explain.

Explain V$TRANSACTION, and usage?
 Explain DBA_ROLLBACK_SEGS, and usage?
 Do we have scripts to monitor the undo growth/usage of the database?

What are the possible causes for excessive undo growth?
 How to resize the undo datafile?
 Drop Undo Tablespace
 What is In Memory Undo?

My Oracle Support provides customers with access to over a million knowledge articles and a vibrant support community of peers and Oracle experts.