hidden parameter change

Oracle Database 12c Enterprise Edition Release 12.1.0.2.0

1/ check the current values:

PARAMETER            IS_DEFAULT SESSION  INSTANCE  IS_SE IS_SYSTEM_MODIFIABLE

-------------------------------- ---------- ---------- ---------- ----- --------------------

_optimizer_enable_extended_stats TRUE    TRUE    TRUE    TRUE IMMEDIATE

2/ change it from true to false:

SQL> alter system set "_optimizer_enable_extended_stats"=false scope=both;

System altered.

3/ check immediately after change:

PARAMETER            IS_DEFAULT SESSION  INSTANCE  IS_SE IS_SYSTEM_MODIFIABLE

-------------------------------- ---------- ---------- ---------- ----- --------------------

_optimizer_enable_extended_stats TRUE    FALSE   FALSE   TRUE IMMEDIATE

4/ let's see if something will be changed after e restart of the DB:

SQL> shu immediate;

SQL> startup