Modifying Optimizer Feature Enabled from 12.2 to 12.1 in CDB Not Effect the Hidden Parameters in PDB (Doc ID 2576953.1)

Last updated on APRIL 17, 2023

Applies to:

Symptoms

• In CDB$ROOT modify optimizer_features_enable from 12.2.0.1 to 12.1.0.2, the relevant hidden parameters (i.e. _optimizer_cbqt_or_expansion) are changed automatically in CDB, but these hidden parameters are not changed in PDB:
  SQL> show con_name

  CON_NAME
  ------------------------------
  CDB$ROOT
  SQL> show parameter optimizer_features_enable

  NAME TYPE VALUE
  ------------------------------------ ----------- ------------------------------
  optimizer_features_enable string 12.2.0.1

  SQL> col "Hidden Parameter" for a50
  SQL> col "Value" for a30

  SQL> select ksppinm as "Hidden Parameter", ksppstvl as "Value" from x$ksppi join x$ksppcv using (indx) where ksppinm = '_optimizer_cbqt_or_expansion';

  Hidden Parameter Value
  -------------------------------------------------- ------------------------------
  _optimizer_cbqt_or_expansion ON

  SQL> alter system set optimizer_features_enable='12.1.0.2' scope=both;

  SQL> select ksppinm as "Hidden Parameter", ksppstvl as "Value" from x$ksppi join x$ksppcv using (indx) where ksppinm = '_optimizer_cbqt_or_expansion';

  Hidden Parameter Value
  -------------------------------------------------- ------------------------------
  _optimizer_cbqt_or_expansion OFF

  SQL> alter session set container=pdb;

  SQL> show parameter optimizer_features_enable;

  NAME TYPE VALUE
  ------------------------------------ ----------- ------------------------------
  optimizer_features_enable string 12.1.0.2
  SQL> select ksppinm as "Hidden Parameter", ksppstvl as "Value" from x$ksppi join x$ksppcv using (indx) where ksppinm = '_optimizer_cbqt_or_expansion';

  Hidden Parameter Value
  -------------------------------------------------- ------------------------------
  _optimizer_cbqt_or_expansion ON <<<<< Still ON

    
  

   

Changes

 None.

Cause

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