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Step 10 - Database Monitoring Through Alerts
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Learn Oracle - Managing Alerts
The following sections describe how to manage alerts.
Viewing Metrics and Thresholds
Metrics are a set of statistics for certain system attributes as defined by Oracle. They
are computed and stored by the AutomaticWorkload Repository, and are displayed on
the All Metrics page, which is viewable by clicking All Metrics under Related Links
heading on the Database Home page (and some other pages).
When Oracle DBA click a specific metric link, a detail page appears, with more information
about the metric. Online help for this page gives Oracle DBA a description of the metric.
Setting Metric Thresholds
Oracle provides a set of predefined metrics, some of which initially have thresholds
defined for them. There may be times when Oracle DBA want to set thresholds for other
metrics, or you want to alter existing threshold settings.
A more general means of setting thresholds is available using the Edit Thresholds
page.
The following steps describe how to set metric thresholds:
1. From the Database Home page, click Manage Metrics under the Related Links
heading.
The Manage Metrics page is displayed. It displays the existing thresholds for
metrics and any response actions that have been specified. Oracle DBA cannot edit any
thresholds on this page.
2. Click Edit Thresholds.
On this page you
can enter newWarning Threshold and Critical Threshold values, or you can
modify existing values. In the Response Actions field, Oracle DBA can enter an operating
system command or a script that you want executed when an alert is issued
because a threshold has been crossed.
For example, to modify the warning threshold for Tablespace Space Used (%) metric,
you can enter 87 as the percentage. Under Response Actions, Oracle DBA can optionally
specify a fully qualified path to an operating system script that will cleanup or
increase the size of the tablespace.
Oracle provides a host of alerts that are not enabled by default. You can enable
them by specifying threshold values. For example, to enable the alert for
Cumulative Logons (for each second), enter 10 for warning and 25 for critical. This
will cause the system to warn you when the number of logons for each second
exceeds 10.
You must click OK to save your changes.
3. For more comprehensive management of threshold settings for the different alerts,
click the radio button in the Select column for that metric, then click Manage
Metric Indexes.
The Manage Metric Indexes:metric_name page is displayed that enables Oracle DBA to add
or delete specific metric threshold and response action settings.
For example, to set the Tablespace Space Used (%) metric thresholds for
individual tablespaces, select this metric then click Manage Metric Indexes. Enter
the tablespace name and its warning and critical values. Click OK.
Setting up Notification
Oracle DBA can optionally direct Enterprise Manager to provide notification when events that
require your intervention arise. For example, if Oracle DBA specify that you want email
notification for critical alerts, and you have a critical threshold set for the system
response time for each call metric, then Oracle DBA could be sent an email containing a message
similar to the following:
Host Name=mydb.us.mycompany.com
Metric=Response Time per Call
Timestamp=08-NOV-2003 10:10:01 (GMT -7:00)
Severity=Critical
Message=Response time per call has exceeded the threshold. See the
lattest ADDM analysis.
Rule Name=
Rule Owner=SYSMAN
The host name is a link to the Database Home page and in the message there is a link
to the latest ADDM analysis.
By default, alerts in critical state such as DB Down, Generic Alert Log Error Status, and
Tablespace Used are set up for notification. However, to receive these notifications,
you must set up your email information.You can do so as follows:
1. From any Database Control page, click the Setup link, which is visible in the
header and footer area.
2. On the Setup page, select Notification Methods.
3. Enter the required information into the Mail Server portion of the Notifications
Methods page. See the online help for assistance.
There are other methods of notification, including scripts and SNMP (Simplified
Network Management Protocol) traps. The latter can be used to communicate
with third-party applications.
4. From any Database Control page, click the Preferences link, which is visible in the
header and footer area.
5. On the Preferences page, select General. Enter your email address in the E-mail
Addresses section.
6. Oracle DBA can optionally edit notification rules, such as to change the severity state for
receiving notification. To do so, select Notification Rules. The Notification Rules
page appears. For more information about configuring notification rules,
When you receive an alert, follow any recommendations it provides, or consider
running ADDM or another advisor, as appropriate to get more detailed diagnostics of
system or object behavior.
For example, if you receive a Tablespace Space Usage alert, Oracle DBA might take a corrective
measure by running the Segment Advisor on the tablespace to identify possible objects
for shrinking. You can then shrink the objects to free space.
Clearing Alerts
Most alerts such as an Out of Space are cleared automatically when the cause of the
problem disappears. However, other alerts such as Generic Alert Log Error are sent to
Oracle DBA for notification and need to be acknowledge by you, the system administrator.
After taking the necessary corrective measures, you can acknowledge an alert by
clearing or purging it. Clearing an alert sends the alert to the Alert History, which is
viewable from the home page under Related Links. Purging an Alert removes it from
the Alert History.
To clear an alert such as Generic Alert Log Error, from the Home page under Alerts,
click the alert link.The Alert Log Errors page appears. Select the alert to clear and click
Clear. To purge an alert, select it and click Purge. Oracle DBA can also Clear Every Open Alert
or Purge Every Alert using these buttons.
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