An item such as a database or a file server may encounter a condition that triggers an alert. An alert is a visual notification to the user that something might possibly go wrong with your server. By way of an example free space in your data files might be approaching zero or CPU usage on your web server might be close to 100%. Conditions that require the user's attention are reported as alerts. Alerts are shown on all views but not every alert is shown on every view and not every alerts may make sense for every item. For instance the data file free space alert does not make sense for a web server and is not triggered for one. All alerts are always reported on Enterprise view where you can see them by clicking on the alert icon next to the item the alert is being reported for.

Internal alerts.  Some conditions may trigger what is called an internal alert. If for example a database server is too busy and does not respond to requests eventually the queue of requests gets overfilled and an internal alert is fired.

Internal alert icon is similar to a regular alert and is placed next to the regular alert icon. Just as a regular alert it shows detailed alert information when clicked and can be closed. Unlike regular alerts internal alerts cannot be configured, disabled and do not have severities.
Sometimes an internal alert text contains an Oracle error code returned by the database. You can find out more about the Oracle error by typing the error code into Oracle Lookup error code box on the toolbar and pressing Enter. You can omit the leading and trailing zeros.