The dba_alert_history table has the
same structure as the dba_outstanding_alerts, except for
the last field. Table 4.4 describes the additional column in the
Resolution -Cleared or N/A
Table 4.4 – Additional column in
There are 161 metrics with definable
threshold values such as physical reads per second, user commits
per second etc. For
example, threshold values can be set so that an alert is sent to
the DBA when the SALES tablespace exceeds 90% threshold warning
level or the 96% critical level.
Alerts can also be stateless or not based
on threshold levels. These stateless alerts are written directly
to the history table and might include “snapshot too old” or
“resumable session has been suspended.” Since OEM stores
stateless alerts in its own repository, clearing the stateless
alerts make sense only in OEM environment.
An alert message will be sent to the SYS
owned predefined persistence queue called alert_que.
Oracle Enterprise Manager (OEM) reads this queue to provide
notifications about outstanding alerts, and may suggest
corrective actions. The alerts are displayed on the Enterprise
Manager console. OEM can be customized to send these messages to
pager or email addresses. If the alert cannot be written to the
queue, a message about the alert will be written to the Oracle
Database alert log.