OPTIMIZER_FEATURES_ENABLE

Property	Description
Parameter type	String
Syntax	OPTIMIZER_FEATURES_ENABLE = { 8.0.0 | 8.0.3 | 8.0.4 | 8.0.5 | 8.0.6 | 8.0.7 | 8.1.0 | 8.1.3 | 8.1.4 | 8.1.5 | 8.1.6 | 8.1.7 | 9.0.0 | 9.0.1 | 9.2.0 | 10.1.0 | 10.1.0.3 | 10.1.0.4 | 10.1.0.5 | 10.1.0.6 | 10.2.0.1 | 10.2.0.2 | 10.2.0.3 | 10.2.0.4 | 10.2.0.5 | 11.1.0.6 | 11.1.0.7 }
Default value	11.1.0.7
Modifiable	ALTER SESSION, ALTER SYSTEM

OPTIMIZER_FEATURES_ENABLE acts as an umbrella parameter for enabling a series of optimizer features based on an Oracle release number.
For example, if you upgrade your database from release 10.1 to release 11.1, but you want to keep the release 10.1 optimizer behavior, you can do so by setting this parameter to 10.1.0. At a later time, you can try the enhancements introduced in releases up to and including release 11.1 by setting the parameter to 11.1.0.6.
Note:
1. Query for the current value of the parameter

select name, value, isdefault, isses_modifiable, issys_modifiable,

isinstance_modifiable, isdeprecated, description

from v$parameter

where upper(name) = ‘OPTIMIZER_FEATURES_ENABLE’;

NAME	VALUE	IS DEFAULT	ISSES_ MODIFIABLE	ISSYS_ MODIFIABLE	ISINSTANCE_ MODIFIABLE	IS DEPRECATED	DESCRIPTION
optimizer_features_enable	10.1.0	FALSE	TRUE	IMMEDIATE	TRUE	FALSE	optimizer plan compatibility parameter

Oracle initializatoin parameters

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