PARALLEL_DEGREE_POLICY is set to
AUTO, this hint enables a statement to bypass the parallel statement queue. However, a statement that bypasses the statement queue can potentially cause the system to exceed the maximum number of parallel execution servers defined by the value of the
PARALLEL_SERVERS_TARGET initialization parameter, which determines the limit at which parallel statement queuing is initiated.
There is no guarantee that the statement that bypasses the parallel statement queue receives the number of parallel execution servers requested because only the number of parallel execution servers available on the system, up to the value of the
PARALLEL_MAX_SERVERS initialization parameter, can be allocated.
SELECT /*+ NO_STATEMENT_QUEUING */ last_name, department_name FROM employees e, departments d WHERE e.department_id = d.department_id;
PARALLEL_DEGREE_POLICY is not set to
AUTO, this hint enables a statement to be considered for parallel statement queuing, but to run only when enough parallel processes are available to run at the requested DOP. The number of available parallel execution servers, before queuing is enabled, is equal to the difference between the number of parallel execution servers in use and the maximum number allowed in the system, which is defined by the
PARALLEL_SERVERS_TARGET initialization parameter.
SELECT /*+ STATEMENT_QUEUING */ last_name, department_name FROM employees e, departments d WHERE e.department_id = d.department_id;