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Don Burleson Blog 







Oracle: Display optimizer features

Oracle Database Tips by Donald BurlesonDecember 24, 2015

Question:  I was just advised by Oracle technical support to fix a SQL bug to adjust my optimizer_features_enable to a 9i optimizer release.  How can I see the history of SQL optimizer bug fixes in 10g?

Answer:  Tracking Oracle features by release is maddening, and I keep a list of major Oracle features by release.   As to optimizer features and bugs, prior to Oracle 11g you had to contact MOSC, but as of 10gr2 and beyond there are two new views v$ststem_fix_control and v$session_fix_control for displaying the specific optimizer features by release of Oracle.

The v$system_fix_control view can be used to display the SQL features of the optimizer by release.  The relevant columns in v$system_fix_control are optimizer_feature_enable, bugno, value, sql_feature and description.  how to display optimizer features by release using v$system_fix_control.

Note the maddening difference between the v$system_fix_control column of optimizer_feature_enable is the anchor that lists the specific detauls by release of Oracle, as opposed to the Oracle parameter optimizer_features_enable, just one letter different and enough to drive the DBA crazy!

To see all of the new SQL optimizer features in Oracle 10g, try the following command:

   substr(optimizer_feature_enable,1,2) = '10'
order by

For a related view, see my notes on v$session_fix_control which is used with Oracle technical support to enable and disable specific optimizer features at the session level

For more detauls, see MOSC note 5483301.8 on using v$system_fix_control.


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