AQ Enqueue / Dequeue Benchmark on RAC 11.1.0.7 Shows Slowdown and Higher CPU

(Doc ID 1105624.1)

Last updated on MAY 04, 2017

Applies to:

Oracle Database - Enterprise Edition - Version 11.1.0.7 and later
Information in this document applies to any platform.

Symptoms

Performance issue affecting AQ applications where they have upgraded to 11.1.0.7 from 10.2.0.4; AQ activity is centred around enqueue / dequeue activity on a RAC environment.

Note : the issue was observed under a benchmark which exibited a slow down of around 20% in enqueue / dequeue performance ; the benchmark was focused specifically on AQ actvity : enqueuing / dequeuing tens of thousands of messages .


It should be stated that most application are unlikely to be affected by the issues below .

Main observations :

- performance degradation with RAC is greater than with single instance;
slow down with single instance is also observed;
- commit activity appears to be taking longer;
- higher CPU observed;
- AWR report indicates higher statistic values in relation to the following for
the same test in 11g :

In the library cache activity ( RAC ) section of the AWR reports there is increased activity with respect to the following (same benchmark test)  :

statistic10.2.0.4 value11.1.0.7 value
ges pin requests 192 603829 ( TABLE )
ges messages sent 2423 5670
global enqueue gets sync 1312577 2315879
global enqueue releases 1309834 2313511

Cause

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