OCP 1Z0 053 210

210.The Database Resource Manager is automatically enabled in the maintenance window that runs the 
Automated Maintenance Task. What is the reason for this? 
A. to prevent the creation of an excessive number of scheduler job classes 
B. to allow the Automated Maintenance Tasks to use system resources without any restriction 
C. to allow resource sharing only among the Automated Maintenance Tasks in the maintenance window 
D. to prevent the Automated Maintenance Tasks from consuming excessive amounts of system resources 
Answer: D 

http://docs.oracle.com/cd/E11882_01/server.112/e25494/tasks.htm#ADMIN0235

About Automated Maintenance Tasks

Automated maintenance tasks are tasks that are started automatically at regular intervals to perform maintenance operations on the database. An example is a task that gathers statistics on schema objects for the query optimizer. Automated maintenance tasks run in maintenance windows, which are predefined time intervals that are intended to occur during a period of low system load. You can customize maintenance windows based on the resource usage patterns of your database, or disable certain default windows from running. You can also create your own maintenance windows.