Query Against DBA_EXTENTS Performs Slowly After Upgrade to 188.8.131.52
(Doc ID 1453425.1)
Last updated on MAY 19, 2022
Applies to:Oracle Database - Enterprise Edition - Version 184.108.40.206 and later
Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Express Cloud 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
Information in this document applies to any platform.
Queries on DBA_EXTENTS are much slower due to the presence of a merge join cartesian.
This can also influence the performance of script used to collect upgrade/migrate diagnostics as per instructions in:
Running script on version 220.127.116.11 prior to upgrade, there was no performance issue.
The following SQL query from dbupgdiag.sql may run slowly (~2 hours) after applying patchset 18.104.22.168.
An execution plan regression occurs if there are a large number of records in the X$KTFBUE table. Gathering of dictionary or fixed object stats does not improve performance as this table is intentionally omitted from those packages.
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