How To Implement And Test Enhanced Statement Queuing In 12c So Critical Statements Bypass The Parallel Statement Queue.
Last updated on APRIL 25, 2014
Applies to:Oracle Database - Enterprise Edition - Version 188.8.131.52 to 184.108.40.206 [Release 12.1]
Information in this document applies to any platform.
In 12.1 Oracle introduces a new resource plan directives called PARALLEL_STMT_CRITICAL which allows critical parallel statements to bypass the parallel statement queue.
There are two options for this directive.
FALSE - The consumer group is non-critical. This is the default value
BYPASS_QUEUE - The consumer group is marked critical, and parallel statements from this consumer group will bypass the parallel statement queue
When set to BYPASS_QUEUE, the parallel statements from the specified consumer group will be executed immediately.
-- More flexibility in controlling critical work.
-- For autodop to work I/O calibration statistics must be gathered.
-- Parallel_degree_policy needs to be set to AUTO or ADAPTIVE to enable statement queuing
Note: With this setting in place it is possible that the number of parallel execution servers may exceed the value of the PARALLEL_SERVERS_TARGET initialization parameter.
The following example shows how to setup and confirm the use of BYPASS_QUEUE for one consumer group and PARALLEL_QUEUE_TIMEOUT for another.
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