Query about Oracle 19c parameters

Question

I am using Oracle 19.0.0 and fired below query.

SELECT * FROM V$SYSTEM_PARAMETER2 

and found below properties are not present.

optimizer_adaptive_features
_optimizer_use_feedback

So my doubt is it is removed in Oracle 19c or renamed it?

I checked it google but no solid reference found.

Thanks in advance.

Answer 1

A (very) quick search lead to a My Oracle Support page for optimizer_adaptive_features:

Changes to adaptive features in 12.2

In 12.2, the parameter optimizer_adaptive_features has been obsoleted, replaced by two new parameters, optimizer_adaptive_plans and optimizer_adaptive_statistics. The optimizer_adaptive_plans parameter controls whether the optimizer creates adaptive plans and defaults to TRUE. The optimizer_adaptive_statistics parameter controls whether the optimizer uses adaptive statistics and defaults to FALSE. The creation of automatic extended statistics is controlled by the table-level statistics preference AUTO_STAT_EXTENSIONS, which defaults to OFF. (AUTO_STAT_EXTENSIONS can be set using DBMS_STATS procedures like SET_TABLE_PREFS and SET_GLOBAL_PREFS.)

These defaults have been chosen to place emphasis on achieving stable SQL execution plans.

Implementing 12.2 adaptive features behavior in 12.1.0.2

The adaptive features changes in 12.2 are available in 12.1.0.2 through a pair of fixes:

• Bug 22652097 splits the parameter optimizer_adaptive_features into two, as above, and disables adaptive statistics by default.
• Bug 21171382 disables the automatic creation of extended statistics unless the statistics preference AUTO_STAT_EXTENSIONS is set to ON.