12-22. Server-generated alerts

A few key metrics that can provide early problem notifications are:

• Average File Read Time (centiseconds)
  
• Dump Area Used (%)
  
• Response Time (per transaction)
  
• SQL Response Time (%)
  
• Tablespace Used (%)
  
• Wait Time (%)

By default, the following server-generated alerts are enabled:

• Tablespace Space Usage (warnings 85%, critical 97%)
  
• Snapshot Too Old
  
• Recovery Area Low on Free Space
  
• Resumable Session Suspended

To set or edit a threshold for your whole database, select Manage Metrics in the Related Links region of the database home page.

There are two kinds of server-generated alerts:

• Threshold (stateful) alerts: they are configured by setting a warning and critical threshold values on database metrics. For example: Physical Reads per second, User commits per second, SQL Service Response Time, etc.
  Except for the Tablespace Space Usage metric, which is database related, the other metrics are instance related.
  Stateful alerts appear in DBA_OUTSTANDING_ALERTS and when cleared, go to DBA_ALERT_HISTORY.
  
• Nonthreshold (stateless) alerts: corresponds to specific database events such as Snapshot Too Old errors, Recovery Area Low On Free Space, and Resumable Session Suspended.
  Stateless alerts go directly to the history table. Clearing a stateless alert makes sense only in the Database Control environment because Database Control stores stateless alerts in its own repository.