OCP 1Z0 053 2

2.You plan to have a larger moving window size for the default system-defined moving window baseline 
because you want to use the adaptive threshold.  
Which statement factors in this consideration while increasing the size of the moving window.? 
A. The collection level for the AWR should be set to BASIC.  
B. The moving window size must be less than Undo Retention. 
C. The moving window size should be greater than the Automatic Workload Repository (AWR) retention 
period. 
D. The moving window size should be equal to or less than the Automatic Workload Repository (AWR) 
retention period. 
Answer: D 

http://docs.oracle.com/cd/E11882_01/server.112/e41573/autostat.htm#PFGRF94179

5.2.2.2 Moving Window Baseline

A moving window baseline corresponds to all AWR data that exists within the AWR retention period. This is useful when using adaptive thresholds because the database can use AWR data in the entire AWR retention period to compute metric threshold values.

Oracle Database automatically maintains a system-defined moving window baseline. The default window size for the system-defined moving window baseline is the current AWR retention period, which by default is 8 days. If you are planning to use adaptive thresholds, consider using a larger moving window—such as 30 days—to accurately compute threshold values. You can resize the moving window baseline by changing the number of days in the moving window to a value that is equal to or less than the number of days in the AWR retention period. Therefore, to increase the size of a moving window, you must first increase the AWR retention period accordingly.