How frequently does the Automatic Database Diagnostic Monitor (ADDM) analysis run by default?

How frequently does the Automatic Database Diagnostic Monitor (ADDM) analysis run by default?

A.
Every 30 minutes

B.
Every 45 minutes

C.
Every 15 minutes

D.
Every 60 minutes

E.
Each time a statspack snapshot is taken

Explanation:
ADDM is invoked automatically every time that a new AWR snapshot is generated (by default every 60 minutes) and the results of the analysis are stored in the AWR repository tagged with the snapshot id. Therefore, the DBA can find historical executions of the advisor and its recommendations.

REF:Note:276103.1 PERFORMANCE TUNING USING 10g ADVISORS AND MANAGEABILITY FEATURES