题目：

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.

参考答案D
解析
题目意思，您计划为默认的系统定义的移动窗口基线设置更大的移动窗口大小。问那个选项是正确的。

参考文档中有答案。

参考文档：

https://docs.oracle.com/cd/E11882_01/server.112/e41573/autostat.htm#PFGRF94177

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.

See Also:

"Modifying the Window Size of the Default Moving Window Baseline" for information about resizing the moving window baseline

https://docs.oracle.com/cd/E11882_01/server.112/e41573/autostat.htm#PFGRF94194

5.3.2.5 Modifying the Window Size of the Default Moving Window Baseline

This section describes how to modify the window size of the default moving window baseline. For information about the default moving window baseline, see "Moving Window Baseline".

To resize the default moving window baseline, use the MODIFY_BASELINE_WINDOW_SIZE procedure:

BEGIN
    DBMS_WORKLOAD_REPOSITORY.MODIFY_BASELINE_WINDOW_SIZE (
                   window_size => 30, 
                   dbid => 3310949047);
END;
/

The window_size parameter is used to specify the new window size, in number of days, for the default moving window size. In this example, the window_size parameter is set to 30. The window size must be set to a value that is equal to or less than the value of the AWR retention setting. To set a window size that is greater than the current AWR retention period, you must first increase the value of the retention parameter, as described in "Modifying Snapshot Settings".

In this example, the optional dbid parameter specifies the database identifier is 3310949047. If you do not specify a value for dbid, then the local database identifier is used as the default value.

END