OpsMgr Answer This: Do I use classes or groups?

We continue our "OpsMgr Answer This" series with a discussion on the new class-based architecture in Operations Manager 2007.

To focus the topic on specific questions, we looked at the following areas:

  • When I select to override a rule or monitor, I can select to target all objects of a class, or all objects in a group. If I have a choice of either (because the objects I am interested in are included in both one or more classes and one or more groups), which should I select?

You would select class. By default, discoveries are targeted at a class; therefore as new objects are added, they will inherit the override. This can be accomplished with groups but discovery will take longer as group membership needs to be calculated also.

  • When I am authoring a management pack, and I want to pre-define how overrides are targeted, is there a performance or feature difference in selecting either classes or groups?

Again, you will want to select class. Targeting groups will prevent you from using DAs (distributed applications) properly. Say you have a monitor targeted at a class, you can add this class to a DA and have its health state roll up.

So when should I use groups over classes?

A situation where targeting groups is easier to administer is when you want to leverage the ability to quickly add and exclude objects from a group using the Authoring space of the Operations console. It’s not so easy to change the membership of a class.

Microsoft provides a video to clarify how targeting a monitor and a group works. The video is available at http://www.microsoft.com/winme/0712/31678/ClarifyTargetingAtGroups_300kbps.asx and is just over a minute long. They have also developed a "poster" of best practices for Rule and Monitor targeting which you can view at http://download.microsoft.com/download/f/a/7/fa73e146-ab8a-4002-9311-bfe69a570d28/BestPractices_Rule_Monitor_REV_110607.pdf. The poster is about 5MB in size.

Key points of the poster:

  • Always target classes unless the objects of interest are only defined by a group
  • Always target the most specific class possible – for example, the Windows 2003 Operating System if all targets are Windows Server 2003, rather than targeting Windows Computer or Windows Server Operating System
  • When you target groups, create a disabled monitor and then enable the monitor for the group.


Here are some other interesting links and additional tidbits (courtesy of Jason Sandys who is helping with the System Center Configuration Manager 2007 Unleashed book):

  • Computer groups cannot per used to target monitors and rules (http://blogs.technet.com/momteam/archive/2007/11/14/targeting-series-part-2-why-targeting-a-computer-group-fails.aspx ), but they can be used to target overrides (http://systemcenterforum.org/wp-content/uploads/OpsMgr_overrides.pdf ). 
  • Normal groups can be used for either targeting scenario depending on the actual objects that are members of the group.  This leads to the conclusion that targeting rules and monitors is completely different from targeting overrides – and it would have been nice if different terms were used for these two types of targeting, maybe filtering for overrides instead of targeting. 
  • Targeting rules and monitors applies them to the actual object and when using the computer group, it actually targets the group object instead of the members of the group but not when using a regular group.  Targeting (filtering) an override always filters based on the members of the group if one is used. 


Do you have burning questions about OpsMgr 2007 you’d like us to answer as part of this series? Please submit those as comments to this article!

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