V$UNDOSTAT MAXQUERYLEN Suddenly Appears With a High Value For a Simple Query (Doc ID 1307600.1)

Last updated on DECEMBER 25, 2016

Applies to:

Oracle Database - Enterprise Edition - Version 10.1.0.2 to 11.2.0.2 [Release 10.1 to 11.2]
Information in this document applies to any platform.
***Checked for relevance on 25-Dec-2016***

Symptoms

Whilst monitoring the MAXQUERYLEN column of V$UNDOSTAT you suddenly see an entry appear with a high value which wasn't shown for the previous time period, and relates to a simple query which should execute relatively quickly, e.g.:

Begin Time       Tuned Retention MaxQueryLen SQL_ID
...
13/03/2011 10:40           64800      168796 0cgwwnqnum22b
13/03/2011 10:30           64800      168193 0cgwwnqnum22b
13/03/2011 10:20           64800      167589 0cgwwnqnum22b
13/03/2011 10:10           64800      166986 0cgwwnqnum22b
13/03/2011 10:00           18000        4210 5j67unxapar3w
...

Cause

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