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Why Didn't My Parallel Query Use the Expected Number of Slaves? (Doc ID 199272.1)

Last updated on SEPTEMBER 30, 2019

Applies to:

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

Purpose

* * * Checked for relevance on 28-April-2010 * * *

This article explains what to check if a query does not use the expected
number of parallel query slaves. It explains :

  1. How to find the number of slaves that were used
  2. What affects the number of query slaves used
  3. How to trace query slave allocation

The word 'query' is used in relation to any type of SQL statement.
The terms 'parallel execution slave', 'parallel slave', 'slave', 'parallel execution server' all mean the same thing.
This article does not cover queries running in an OPS environment.

Troubleshooting Steps

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In this Document
Purpose
Troubleshooting Steps
 1./ How to find the number of slaves that were used
 1a. From the same session as the query
 1b. From a different session
 2. What affects the number of query slaves used
 1. PARALLEL_MAX_SERVERS
 2. PARALLEL_MIN_PERCENT
 3. PARALLEL_AUTOMATIC_TUNING
 4. PARALLEL_ADAPTIVE_MULTI_USER
 6. Resource Manager
 3. How to trace query slave allocation
References

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