===== Concurrent Statistics =====
Utilises three components
  * Scheduler
  * Advanced Queueing
  * Resource Manager

==== Enabling ====
  * JOB_QUEUE_PROCESSES parameter must be set to at least 4
  * Resource Manager must be enabled
  * CONCURRENT preference of the DBMS_STATS.SET_GLOBAL_PREFS must be MANUAL, AUTOMATIC or ALL

Enable the Resource Manager by specifying a resource plan\\
<code>SQL> ALTER SYSTEM SET RESOURCE_MANAGER_PLAN = 'DEFAULT_PLAN';</code>
Set the JOB_QUEUE_PROCESSES parameter to a value at least twice the number of CPU cores\\
<code>SQL> ALTER SYSTEM SET JOB_QUEUE_PROCESSES = 8;</code>
Enable Concurrent Statistics by executing the SET_GLOBAL_PREFS procedure\\
<code>BEGIN
  DBMS_STATS.SET_GLOBAL_PREFS('CONCURRENT','ALL');
END;
/</code>
Check it is enabled by issuing the following query\\
<code>SELECT DBMS_STATS.GET_PREFS('CONCURRENT') FROM DUAL;</code>
After starting a manual or automatic statistics gathering job, you can monitor it
<code>SELECT target, target_type, job_name, to_char(start_time, 'DD-MON-YYYY HH24:MI:SS') time_started
FROM dba_optstat_operation_tasks
WHERE status = 'IN PROGRESS'
AND opid = (SELECT max(id) FROM dba_optstat_operations
            WHERE operation = 'gather_schema_stats');</code>