Concurrent SQL Statements Run Slower in 12c When Compared to 11g
(Doc ID 2097729.1)
Last updated on DECEMBER 05, 2019
Applies to:Oracle Database - Enterprise Edition - Version 18.104.22.168 to 22.214.171.124 [Release 12.1]
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 Backup Service - Version N/A and later
Information in this document applies to any platform.
- Performance of the concurrent SQL statements degrade after an upgrade to database version 12c.
- The same concurrent SQL statements executed optimally with an expected response time in the 11g environment prior to the upgrade.
- The execution plan for the concurrent SQL statements changed after the upgrade to 12c.
- Setting the OPTIMIZER_FEATURES_ENABLE parameter to 126.96.36.199 or 188.8.131.52 results in a good plan and expected response time.
- Issue is related to Adaptive Query Optimization features.
<Document 2031605.1> - Adaptive Query Optimization
Database upgrade from 11g to 12c using the default 12c database configuration settings for optimizer related parameters.
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