Real-Time Database Operation Monitoring is actually a synonymous term of SQL Monitoring for Enterprise Manager (either Cloud Control or Grid Control). Therefore, its features and purposes are all around monitoring the performance of SQL, such as the following operations:
Expensive SQL statements.
Long-running stored procedures.
Batch jobs (either from scheduler or applications).
ETL or Reporting.
Here are the tasks and purposes listed in official documentation when using SQL Monitoring.
Tracking and reporting
Monitoring execution progress
Monitoring resource usage
Tuning for response time
Any moment of the above, you can enable real-time database operation monitoring. But STATISTICS_LEVEL initialization parameter must be either set to TYPICAL (the default value) or ALL.
For specific composite database operations, you may create a database operation by package DBMS_SQL_MONITOR. For further information, you may refer to the following documentation: Monitoring Real-Time Database Operations