In Essentials 2007, monitors can be used to assess various conditions that can occur in monitored objects. For example, a monitor can be used to assess the values of a performance counter, the existence of an event, the occurrence of data in a log file, the status of a Windows Service, or the occurrence of a Simple Network Management Protocol (SNMP) trap. The result of this assessment determines the health state of a target and the alerts that are generated. You can use three different types of monitors for these assessments: unit monitors, aggregate rollup monitors, or dependency rollup monitors.

Unit Monitor

Unit monitors, the fundamental monitoring components, are used to monitor specific counters, events, scripts, and services. Unit monitors can be rolled up to either dependency or aggregate rollup monitors. You have the option to set the monitor to generate an alert.

Aggregate Rollup Monitor

An aggregate rollup monitor reflects the state of unit, dependency rollup, or other aggregate rollup monitors targeted to an object. You typically use an aggregate rollup monitor to group multiple monitors into one monitor and then use that monitor to set the health state and generate an alert.

Each target in Essentials 2007 contains the following top-level aggregate rollup monitors that you can use to group monitors of similar type for reporting purposes:

  • Availability

  • Configuration

  • Performance

  • Security

Dependency Rollup Monitor

A dependency rollup monitor rolls up health states from targets linked by either a hosting or a membership relationship. Hosting and membership relationships for a given target are defined in most Management Packs. Like an aggregate rollup monitor, a dependency rollup monitor can be used to group other monitors to set the health state and generate alerts.

For example, consider a Microsoft SQL Server installation consisting of multiple databases. A hierarchy of targets starts with Windows Computer. The Windows Computer object hosts the SQL Server object. The SQL Server object hosts multiple databases. The health status of individual targets (for example, the SQL Server target) is monitored using a combination of aggregate rollup and unit monitors. Without a dependency rollup monitor, you would be unable to roll up the state of the SQL Server target up to the Windows Computer target.

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