Hello Ali,
This forum is for System Center Essentials(SCE) related issues. For questions about System Center Operations Manager(SCOM), please use the following Forums, which would be the best resource for your question.
System Center Operations Manager Forums
http://social.technet.microsoft.com/Forums/en-CA/operationsmanagergeneral/threads
Please also refer to the article for more information:
Agent and Agentless Monitoring
Yog Li -- Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.