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Should you enable _fix_controls with DBMS_OPTIM_BUNDLE?

Today, Paul mailed me asking a question we internally discussed many times in the past weeks: Should you enable _fix_controls with DBMS_OPTIM_BUNDLE? And there is no easy simple answer. But I can give a recommendation based on my experience from many projects.

DBMS_OPTIM_BUNDLE – a quick recap

Just in case you haven’t dealt with DBMS_OPTIM_BUNDLE recently, here is a quick recap.

With below procedure, you can list the available potentially behavior changing optimizer fixes in the current patch bundle – and you can turn them on or off at will:

SQL> set serveroutput on;
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Oracle 12.2 and higher: Set _cursor_obsolete_threshold to old default

Sometimes development groups change default parameter settings because it fits well for a specific feature. This has happened with _cursor_obsolete_threshold in Oracle Database 12.2. But there’s now an official recommendation for Oracle 12.2 and higher: Set _cursor_obsolete_threshold to old default.

What is _cursor_obsolete_threshold?

First of all, this is obviously an underscore parameter. And usually the policy is: Don’t change underscore parameters unless either you clearly understand what you are changing. Or unless Oracle Support (or another Oracle authority) advises you to do.

Oracle 12.2 and higher: Set _cursor_obsolete_threshold to old default

Photo by Jakub Gorajek on Unsplash

We introduced this parameter in Oracle 11.2.0.3 for an issue of growing

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