Today i stubled upon a, somewhat older, but rather interesting blog post of Raphael Burri. He wrote an extensive article about creating dynamic groups in Operations Manager and what the impact is on the Root Management Server (RMS).
Raphael created some pdf's with examples of how you can create more advanced membership rules for dynamic groups.
When you use the Operations Manager Console for creating groups you may find that you're pretty limited in using more complex constuctions, like using contains/not contains expression in the membership element clauses.
Instance and Computer Groups
When you look closer to the XML code that is created when exporting a MP with a 'OC'-created Group in it, you will notice that those groups are always instanced from the InstanceGroup class.
Taking a peek at all your groups in the OC, shows Computer Groups besides the Instance Groups. What's the difference? The icon :P and the relationship type. A Computer Groups only contains computer whereas an Instance Group can contain all types of objects.
Micrsoft uses both Group type in various management packs, like the IIS and Exchange 2007 MP.
Asking around gives me the impression almost everybody is just using Instance Groups. But DO know that other group types (classes) are available.
Link to Raphael Burri's post: http://rburri.wordpress.com/2009/01/14/dynamic-group-membership-authoring-and-performance-impact-on-rms/
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