What are Oracle Database Metrics?

Oracle Database Metrics are statistical values collected by the database kernel, providing insight into system performance. They are typically measured as rates per unit of time (second), per transaction, or per session. These metrics form the foundation of Oracle's performance monitoring infrastructure. The database can be configured with thresholds for these metrics; when a threshold is crossed, a server-generated alert is created. This allows for proactive performance management by automatically detecting and notifying administrators of potential issues.

B. Metrics are the data used for monitoring; the notification system is a separate component that acts on alerts generated from metrics, but they are not part of it.
D. This incorrectly states metrics are part of the EM notification system. Metrics are generated by the database; EM is a tool that consumes and acts on them.
E. Metrics are generated by the database itself, not "built in" Oracle Enterprise Manager. EM is a management tool that collects and displays these metrics.

1. Oracle Database 23ai, Performance Tuning Guide, Chapter 5, "Automatic Performance Diagnostics". It defines metrics as "statistics that are measured over a time interval."

2. Oracle Database 23ai, Administrator's Guide, Chapter 8, "Monitoring the Database", Section "Managing Server-Generated Alerts". It states, "The Oracle Database server provides a monitoring infrastructure that is based on metrics... When a metric value crosses a server-defined threshold, the server generates an alert."

3. Oracle Database 23ai, Reference, "V$SYSMETRIC". This view description details the system-level metrics captured by the database, such as 'Physical Reads Per Sec' and 'User Commits Per Sec'.