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How to Monitor the Parallel Statement Queue (Doc ID 1684985.1)

Last updated on NOVEMBER 07, 2023

Applies to:

Oracle Database Cloud Exadata Service - Version N/A and later
Oracle Database Backup Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Oracle Database Cloud Service - Version N/A and later
Oracle Database Cloud Schema Service - Version N/A and later
Information in this document applies to any platform.

Goal

When the parameter PARALLEL_DEGREE_POLICY is set to AUTO, Oracle Database queues SQL statements that require parallel execution if the necessary parallel server processes are not available. After the necessary resources become available, the SQL statement is dequeued and allowed to execute. The default dequeue order is a simple first in, first out queue based on the time a statement was issued. 

The following is a summary of parallel statement processing.

  1. A SQL statements is issued.

  2. The statement is parsed and the DOP is automatically determined.

  3. Available parallel resources are checked.

    1. If there are enough parallel resources and there are no statements ahead in the queue waiting for the resources, the SQL statement is executed.

    2. If there are not enough parallel servers, the SQL statement is queued based on specified conditions and dequeued from the front of the queue when specified conditions are met.

This note provides a query, so you can monitor statements that are in the parallel statement queue.

Solution

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In this Document
Goal
Solution
References

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