How to change the start time for a maintenance window

For example, if you want to change the start time for the MONDAY_WINDOW from the default 22:00 to 23:59, use the following syntax:

BEGIN
DBMS_SCHEDULER.DISABLE(name=>'"SYS"."MONDAY_WINDOW"',force=>TRUE);
END;
/

BEGIN
DBMS_SCHEDULER.SET_ATTRIBUTE(name=>'"SYS"."MONDAY_WINDOW"',attribute=>'REPEAT_INTERVAL',value=>'FREQ=WEEKLY;BYDAY=MON;BYHOUR=23;BYMINUTE=59;BYSECOND=0');
END;
/

BEGIN
DBMS_SCHEDULER.ENABLE(name=>'"SYS"."MONDAY_WINDOW"');
END;
/