Oracle: Parallel Statement Queuing

If parallel_degree_policy is set to auto (or also adaptive?) or a parallel hint is used, and an SQL statement is requested to be executed in parallel, but the sum of requested and already executing parallel servers exceeds the value of parallel_servers_target, the statement is queued until sufficient servers are available.

Statements are queued with the FIFO principle.

It is possible, however, to run a queued statement immediately with dbms_resource_manager.dequeue_parallel_statement.

In addition, it's possible to assign priorities to consumer groups (Package dbms_resource_manager, procedures create_plan_directive and update_plan_directive).

Queued statements are waiting for the resmgr:pq queued event.

Statements executed by users haveing the database resource manager directive parallel_statement_criticial set to bypass_queue bypass the statement queue.

select
   name,
   value
from
   v$parameter
where
   name in (
       'parallel_degree_policy',
       'parallel_servers_target'
   );

select
   sql_id,
   sql_text
-- ‥
from
   v$sql_monitor
where
   status = 'QUEUED';