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Query Against DBA_EXTENTS Performs Slowly After Upgrade to (Doc ID 1453425.1)

Last updated on MAY 19, 2022

Applies to:

Oracle Database - Enterprise Edition - Version 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:

<Document 556610.1> Script to Collect DB Upgrade/Migrate Diagnostic Information (dbupgdiag.sql) .

Running script  on version prior to upgrade, there was no performance issue.
The following SQL query from dbupgdiag.sql may run slowly  (~2 hours) after applying patchset



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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