Setting Metric Thresholds for Performance Alerts

A metric is the rate of change in a cumulative statistic. This rate can be measured against a variety of units, including time, transactions, or database calls. For example, the number of database calls per second is a metric. You can set thresholds on a metric so that an alert is generated when the threshold is passed.

Performance alerts are based on metrics that are performance-related. These alerts are either environment-dependent or application-dependent.

Environment-dependent performance alerts may not be relevant on all systems. For example, the AVERAGE_FILE_READ_TIME metric generates an alert when the average time to read a file exceeds the metric threshold. This alert may be useful on a system with only one disk. On a system with multiple disks, however, the alert may not be relevant because I/O processing is spread across the entire subsystem.

Application-dependent performance alerts are typically relevant on all systems. For example, the BLOCKED_USERS metric generates a performance alert when the number of users blocked by a particular session exceeds the metric threshold. This alert is relevant regardless of how the environment is configured.

To obtain the most relevant information from performance alerts, set the threshold values of performance metrics to values that represent desirable boundaries for your system. You can then fine-tune these values over time until your system meets or exceeds your performance goals.

To set thresholds for performance metrics:

Access the Database Home page.

See "Accessing the Database Home Page" for more information.
From the Oracle Database menu, select Monitoring, and then Metric and Collection Settings.

If the Database Login page appears, then log in as a user with administrator privileges. The Metric Settings page appears.
For each performance metric relevant for your system, click the Edit icon.

The Edit Advanced Settings page appears.
Follow the steps of the wizard to set the threshold value.