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Automatic Tuning of Undo Retention Common Issues (Doc ID 1579779.1)

Last updated on DECEMBER 30, 2019

Applies to:

Oracle Database - Enterprise Edition - Version 12.1.0.2 to 12.1.0.2 [Release 12.1]
Oracle Database - Enterprise Edition - Version 10.2.0.1 to 11.2.0.4 [Release 10.2 to 11.2]
Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Information in this document applies to any platform.

Purpose

This document is intended to address the most popular and common issues with the Automatic Tuning of Undo Retention. Oracle Database automatically tunes the undo retention period based on how the undo tablespace is configured.
o If the undo tablespace is configured with the AUTOEXTEND option, the database dynamically tunes the undo retention period to be somewhat longer than the longest-running active query on the system.
o If the undo tablespace is fixed size, the database dynamically tunes the undo retention period for the best possible retention for that tablespace size and the current system load. This best possible retention time is typically significantly greater than the duration of the longest-running active query.

For more infomration, please visit the Oracle Documentation Guide found via the following link:
http://docs.oracle.com/cd/B28359_01/server.111/b28310/undo002.htm

Troubleshooting Steps

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In this Document
Purpose
Troubleshooting Steps
 Automatic Tuning of Undo Retention Feature
 Common Issues
  1- Space Related Issues/ Undo Tablespace is Full
 a. Expected behavior/ Concepts Misunderstanding:
 b. wrong calculation of the tuned undo retention value
 2- Undo Remains Unexpired and TUNED_UNDORETENTION is high
 Further Diagnostics
References

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