Enable oracle 11g to automatically collect statistics

Today, I received a case from my friend database. When I created a database in DBCA, I removed the option of automatic statistics collection. The database has not collected statistics for six months. The method to enable this feature is as follows:

Exec DBMS_AUTO_TASK_ADMIN.ENABLE ();
Exec DBMS_AUTO_TASK_ADMIN.ENABLE (client_name => 'Auto optimizer stats collection ', operation => 'Auto optimizer stats job', window_name => null );
Exec DBMS_AUTO_TASK_ADMIN.ENABLE (client_name => 'Auto optimizer stats collection ', operation => NULL, window_name => NULL );
 
 
Select window_name,
Window_next_time,
Optimizer_stats,
Aa. WINDOW_ACTIVE,
Aa. SEGMENT_ADVISOR,
Aa. AUTOTASK_STATUS,
Aa. OPTIMIZER_STATS
From dba_autotask_window_clients aa
Order by window_next_time