The oracle optimizer

The optimizer is influenced by its decision by the following factors:

1. OPTIMIZER_MODE in the initialization file
2. statistics in the data dictionary
3. OPTIMIZER_GOAL parameter of the ALTER SESSION statement
   • CHOOSE
   • ALL_ROWS
   • FIRST_ROWS
   • RULE
4. hints

Use the following select statement if you want to query about the current optimizer mode in use:

select value from v$parameter where name='optimizer_mode'

Use the following alter session command to change the optimizer mode to rule:

alter session set optimizer_mode='rule'