Setting Automatic Degree of Parallelism Using Hints

You can use the PARALLEL hint to force parallelism. It takes an optional parameter: the DOP at which the statement should run. In addition, the NO_PARALLEL hint overrides a PARALLEL parameter in the DDL that created or altered the table.The following example illustrates forcing the statement to be executed in parallel:

SELECT /*+parallel */ last_name, department_name 
       FROM employees e, departments d 
       WHERE e.department_id=d.d.department_id;

The following example illustrates forcing the statement to be executed in parallel with a degree of 10:

SELECT /*+ parallel(10) */ last_name, department_name 
       FROM employees e, departments d 
       WHERE e.department_id=d.department_id;

The following example illustrates forcing the statement to be executed serially:

SELECT /*+ no_parallel */ last_name, department_name 
       FROM employees e, departments d 
       WHERE e.department_id=d.department_id;

The following example illustrates computing the DOP the statement should use:

SELECT /*+ parallel(auto) */ last_name, department_name
       FROM employees e, departments d 
       WHERE e.department_id=d.department_id;

The following example forces the statement to use Oracle Database 11g Release 1 (11.1) behavior:

SELECT /*+ parallel(manual) */ last_name, department_name
       FROM employees e, departments d 
       WHERE e.department_id=d.department_id;