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Step 10 - Database Monitoring Through Alerts

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)


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.
Oracle Tutorial - BLOGS

STEP 10 - Next Topics
Monitoring the health of a database and ensuring that it performs optimally is an important task for a database administrator. This discusses the features and functionality included in Oracle Database that make it easy to proactively monitor database health, identify performance problems, and implement any corrective actions. Click on Oracle tuorial links below:
Proactive Database MonitoringDatabase Monitoring
Oracle Diagnosing Performance Problems
Using Advisors to Optimize Database Performance
Oracle Database - PODCASTS
More Tutorials on Oracle dba ...

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Source : Oracle Documentation | Oracle DBA

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