OCP 1Z0 053 30

30.Which two statements are true with respect to the maintenance window? (Choose two.) 
A. A DBA can enable or disable an individual task in all maintenance windows. 
B. A DBA cannot change the duration of the maintenance window after it is created. 
C. In case of a long maintenance window, all Automated Maintenance Tasks are restarted every four 
hours. 
D. A DBA can control the percentage of the resource allocated to the Automated Maintenance Tasks in 
each window. 
Answer: AD 

http://docs.oracle/cd/B28359_01/server.111/b28310/tasks003.htm#ADMIN12497

Enabling and Disabling Maintenance Tasks for Specific Maintenance Windows

By default, all maintenance tasks run in all predefined maintenance windows. You can disable a maintenance task for a specific window. The following example disables the Automatic SQL Tuning Advisor from running in the windowMONDAY_WINDOW:

BEGIN
dbms_auto_task_admin.disable(
    client_name => 'sql tuning advisor', 
    operation   => NULL, 
    window_name => 'MONDAY_WINDOW');
END;

Changing Resource Allocations for Automated Maintenance Tasks

To change the resource allocation for automated maintenance tasks within a maintenance window, you must change the percentage of resources allocated to the subplan ORA$AUTOTASK_SUB_PLAN in the resource plan for that window. (By default, the resource plan for each predefined maintenance window is DEFAULT_MAINTENANCE_PLAN.) You must also adjust the resource allocation for one or more other subplans or consumer groups in the window's resource plan such that the resource allocation at the top level of the plan adds up to 100%. For information on changing resource allocations, see Chapter 25, "Managing Resource Allocation with Oracle Database Resource Manager".