Re: US Enqueue , latch row object cache - performance issue
Date: Tue, 11 Aug 2009 11:13:20 -0700 (PDT)
On Aug 11, 12:35 pm, Grzegorz <grzegor..._at_interia.pl> wrote:
> one of our 126.96.36.199 EE databse suffered from US enqueue contention.
> Scenario was:
> 1. NOSPACEERRCNT in v$undostat suddenly showed 200 with high UNX% EXP%
> columns values (10 000 - 20 000)
> 2. v$session_wait showed about 30 session with enqueue US type waits and
> about 22 latch waits (type row cache object )
> Best regards.
Take a look at Metalink Doc ID 463136.1 "POOR PERFORMANCE DUE TO HUGE WAITS ON US ENQUEUE" which applies to versions 188.8.131.52 to 184.108.40.206. Doc ID 301432.1 "Performance Slowdown During Heavy Undo Segment Onlining" states that it applies to 220.127.116.11, but the work-around is almost the same as for Doc ID 463136.1.
An advanced Metalink search for the phrase "US enqueue" finds several other related documents.
IT Manager/Oracle DBA
K&M Machine-Fabricating, Inc. Received on Tue Aug 11 2009 - 13:13:20 CDT