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

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

D.
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.

Explanation:
* Monitoring database operations
Real-Time Database Operations Monitoring enables you to monitor long running
database tasks such as batch jobs, scheduler jobs, and Extraction, Transformation,
and Loading (ETL) jobs as a composite business operation. This feature tracks the
progress of SQL and PL/SQL queries associated with the business operation being
monitored. As a DBA or developer, you can define business operations for
monitoring by explicitly specifying the start and end of the operation or implicitly
with tags that identify the operation.