AUTOTASK

To check the autotask are enable 

SQL> select client_name,status from dba_autotask_client;

CLIENT_NAME                                                      STATUS
---------------------------------------------------------------- --------
auto optimizer stats collection                                  ENABLED
auto space advisor                                               ENABLED
sql tuning advisor                                               ENABLED

To enable automatic statistics collection

BEGIN
  DBMS_AUTO_TASK_ADMIN.ENABLE(
    client_name => 'auto optimizer stats collection',
    operation => NULL,
    window_name => NULL);
END;

/

To disable automatic statistics collection

BEGIN
   dbms_auto_task_admin.disable
             (client_name=> 'auto optimizer stats collection',
              operation        => NULL,
              window_name      => NULL
             );
END;

Auto Optimizer Stats Collection Autotask
exec DBMS_AUTO_TASK_ADMIN.ENABLE(client_name => 'auto optimizer stats collection',operation => NULL,window_name => NULL);

exec DBMS_AUTO_TASK_ADMIN.DISABLE(client_name => 'auto optimizer stats collection',operation => NULL,window_name => NULL);

Auto Space Advisor Autotask
exec DBMS_AUTO_TASK_ADMIN.ENABLE (client_name => 'auto space advisor',operation => NULL,window_name => NULL);

exec DBMS_AUTO_TASK_ADMIN.DISABLE(client_name => 'auto space advisor',operation => NULL,window_name => NULL);

Sql Tuning Advisor Autotask
exec DBMS_AUTO_TASK_ADMIN.ENABLE (client_name => 'sql tuning advisor',operation => NULL,window_name => NULL);


exec DBMS_AUTO_TASK_ADMIN.DISABLE(client_name => 'sql tuning advisor',operation => NULL,window_name => NULL);