Thursday Feb 27, 2014

Fast Recovery Area for Archive Destination


If you are using Fast Recovery Area (FRA) for the archive destination and the destination is set to USE_DB_RECOVERY_FILE_DEST, you may notice that the Archive Area % Used metric does not trigger anymore. Instead you will see the Recovery Area % Used metric trigger when it hits a Warning threshold of 85% full, and Critical of 97% full. As this metric is controlled by the server side database thresholds it cannot be modified by Enterprise Manager (see MOS Note 428473.1 for more information). Thresholds of 85/97 are not sufficient for some of the larger, busier databases. This may not give you enough time to kickoff a backup and clear enough logs before the archiver hangs. If you need different thresholds, you can easily accomplish this by creating a Metric Extension (ME) and setting thresholds to your desired values.  This blog will walk through an example of creating an ME to monitor archive on FRA destinations, for more information on ME's and how they can be used, refer to the Oracle Enterprise Manager Cloud Control Administrator's Guide

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Tuesday Feb 18, 2014

Monitoring Archive Area % Used on Cluster Databases


One of the most critical events to monitor on an Oracle Database is your archive area. If the archive area fills up, your database will halt until it can continue to archive the redo logs. If your archive destination is set to a file system, then the Archive Area % Used metric is often the best way to go. This metric allows you to monitor a particular file system for the percentage space that has been used. However, there are a couple of things to be aware of for this critical metric.

Cluster Database vs. Database Instance

You will notice in EM 12c, the Archive Area metric exists on both the Cluster Database and the Database Instance targets. The majority of Cluster Databases (RAC) are built against database best practices which indicate that the Archive destination should be shared read/write between all instances. The purpose for this is that in case of recovery, any instance can perform the recovery and has all necessary archive logs to do so. Monitoring this destination for a Cluster Database at the instance level caused duplicate alerts and notifications, as both instances would hit the Warning/Critical threshold for Archive Area % Used within minutes of each other. To eliminate duplicate notifications, the Archive Area % Used metric for Cluster Databases was introduced. This allows the archive destination to be monitored at a database level, much like tablespaces are monitored in a RAC database.

In the Database Instance (RAC Instance) target, you will notice the Archive Area % Used metric collection schedule is set to Disabled.

If you have a RAC database and you do not share archive destinations between instances, you will want to Disable the Cluster Database metric, and enable the Database Instance metric to ensure that each destination is monitored individually.


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