OCP 1Z0 052 46

46. Which two statements are true about the Automatic Database Diagnostic Monitor (ADDM)? (Choose two.) 
A.The ADDM requires at least four AWR snapshots for analysis. 
B.The ADDM runs after each AWR snapshot is collected automatically by MMON.  
C.The results of the ADDM analysis are stored in the Automatic Workload Repository (AWR). 
D.The ADDM analysis provides only diagnostic information but does not provide recommendations. 
E.The ADDM calls other advisors if required, but does not provide recommendations about the advisors. 
Answer: BC

A 

http://docs.oracle.com/cd/E11882_01/server.112/e41573/diag.htm#PFGRF94240

The time period analyzed by ADDM is defined by the last two snapshots (the last hour by default).

D E

http://docs.oracle.com/cd/E11882_01/server.112/e40540/cncptdba.htm#CNCPT850

Automatic Database Diagnostic Monitor (ADDM) is a self-diagnostic advisor built into Oracle Database. Using statistics captured in AWR, ADDM automatically and proactively diagnoses database performance and determines how identified problems can be resolved. You can also run ADDM manually.

ADDM takes a holistic approach to system performance, using time as a common currency between components. ADDM identifies areas of Oracle Database consuming the most time. For example, the database may be spending an excessive amount of time waiting for free database buffers. ADDM drills down to identify the root cause of problems, rather than just the symptoms, and reports the effect of the problem on Oracle Database overall. Minimal overhead occurs during the diagnostic process.

In many cases, ADDM recommends solutions and quantifies expected performance benefits. For example, ADDM may recommend changes to hardware, database configuration, database schema, or applications. If a recommendation is made, then ADDM reports the time benefit. The use of time as a measure enables comparisons of problems or recommendations.

Besides reporting potential performance issues, ADDM documents areas of the database that are not problems. Subcomponents such as I/O and memory that are not significantly impacting database performance are pruned from the classification tree at an early stage. ADDM lists these subcomponents so that you can quickly see that there is little benefit to performing actions in those areas.