How do you accomplish this?

You upgraded from a previous Oracle database version to Oracle Database version to
Oracle Database 12c. Your database supports a mixed workload. During the day, lots of
insert, update, and delete operations are performed. At night, Extract, Transform, Load
(ETL) and batch reporting jobs are run. The ETL jobs perform certain database operations
using two or more concurrent sessions. After the upgrade, you notice that the performance
of ETL jobs has degraded. To ascertain the cause of performance degradation, you want to
collect basic statistics such as the level of parallelism, total database time, and the number
of I/O requests for the ETL jobs. How do you accomplish this?

A.
Examine the Active Session History (ASH) reports for the time period of the ETL or batch
reporting runs.

B.
Enable real-time database operation monitoring using the
DBMS_SQL_MONITOR.BEGIN_OPERATION function, and then use the
DBMS_SQL_MONITOR.REPORT_SQL_MONITOR function to view the required
information.

C.
Enable SQL tracing for the queries in the ETL and batch reporting queries and gather
diagnostic data from the trace file.

D.
Enable real-time SQL monitoring for ETL jobs and gather diagnostic data from the
V$SQL_MONITOR view.