plsql_optimize_level and plsql_code_type parameters

Purpose
We are able to use plsql_optimize_level parameter for getting better execution performance on plsql codes. On the other way, plsql_code_type parameter is using to change compilation mode.

Usage
Check current parameter:
SQL> show parameter plsql

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
plsql_ccflags                        string
plsql_code_type                      string      INTERPRETED
plsql_debug                          boolean     FALSE
plsql_optimize_level                 integer     2
plsql_v2_compatibility               boolean     FALSE
plsql_warnings                       string      DISABLE:ALL

Apply the setting:
init.ora file:
*.plsql_optimize_level=3
*.plsql_code_type='NATIVE'

SQL> shutdown immediate;

SQL> startup upgrade;

SQL> @$ORACLE_HOME/rdbms/admin/dbmsupgnv.sql;

SQL> shutdown;

SQL> startup;

SQL> ALTER SYSTEM ENABLE RESTRICTED SESSION;

SQL> @$ORACLE_HOME/rdbms/admin/utlrp.sql;

SQL> ALTER SYSTEM DISABLE RESTRICTED SESSION;

Check lastly:
SQL> show parameter plsql

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
plsql_ccflags                        string
plsql_code_type                      string      NATIVE
plsql_debug                          boolean     FALSE
plsql_optimize_level                 integer     3
plsql_v2_compatibility               boolean     FALSE
plsql_warnings                       string      DISABLE:ALL

To see current status of objects;
SQL> 
SELECT TYPE, PLSQL_CODE_TYPE, COUNT(*) FROM DBA_PLSQL_OBJECT_SETTINGS
WHERE PLSQL_CODE_TYPE IS NOT NULL
GROUP BY TYPE, PLSQL_CODE_TYPE
ORDER BY TYPE, PLSQL_CODE_TYPE;

Deep notes
INTERPRETED -> PL/SQL library units compile as bytecode format
NATIVE -> PL/SQL library units compile as native (machine) code format

Ref: https://becomeadba.com/?pages-list