IF: Undo Wait Event - Enq: US - contention (Doc ID 1951680.1)

Last updated on MAY 22, 2017

Applies to:

Oracle Database - Enterprise Edition - Version 9.2.0.1 and later
Information in this document applies to any platform.
*** Checked for relevance on 05-Apr-2016 ***

Symptoms

AWR reports shows enq: US - contention as the top or latch: row cache objects as top with enq: US - contention as one of the Top 5 wait events
                    
Event                                 Waits    Time (s)   (ms)   Time Wait    
 
------------------------------ ------------ ----------- ------ ------                  
latch: row cache objects          2,057,004     490,074    238   43.8 Concurrency                  
enq: US - contention              1,548,328     370,460    239   33.1   Other        

Or when you investigate and found enq: US - contention is the cause of the performance of a session/database.

Cause

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