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OR Dear Me!  When Cost Based OR  Expansion Gets it Wrong – Part 2

I promised in Part 1 that next we would drill into where the cardinality estimate for the non-transformed query comes about, but, never having been someone to refrain from kicking the Cost Based Optimizer when it’s down, I realised i can fool it even better with some skewed data, and a histogram. Note I am …

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OR Dear Me!  When Cost Based OR  Expansion Gets it Wrong – Part 1

The Cost Based OR Expansion transformation allows the optimizer to generate execution plans which often perform better than could be otherwise achieved. But sometimes, as in a case I have been recently investigating, it can cause things to go wrong.  I have modeled the behavior and will demonstrate in it this article.  Planned subsequent articles …

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ords.enable_schema fails with “ORA-06598: insufficient INHERIT PRIVILEGES privilege”

This is issue I always hit settitng up a test environment using Oracle REST Data Services (ORDS).  Using SYSTEM user to call ords.enable_schema throws ORA-06598.  According to the documentation it should succeed (note the SYSTEM user has DBA role) . Only database users with the DBA role can enable or disable a schema other than their …

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ORA-01017 starting DB with srvctl? Consider firing your (oracle) agent!

Warning please don’t blindly follow the steps here without doing your own analysis of the risks involved, and ideally without getting Oracle support involved, I was hesitant to publish this, but as I’ve been in contact with someone else and it’s helped them workaround (to some extent) an issue they have been having I think …

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SQL Plan Directives: Gotta Purge ‘Em All

A tip I picked up from Nigel Bayliss regards purging SQL Plan Directives, I’ve been using it a lot recently and can’t see it documented elsewhere. As some background these records, exposed via the DBA_SQL_PLAN_DIRECTIVES view, are cardinality corrections created and used when running with Adaptive Statistics enabled.  There is a job that should automatically …

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