System Center Operations Manager relies on AD DS for a number of services, including definition of security principles, rights assignment, authentication, and authorization. Operations Manager queries AD DS when performing computer and service discovery and can use AD DS for storing and distributing agent configuration information. For Operations Manager to function properly, AD DS and its supporting service, DNS, need to be healthy and at certain minimum configuration levels. In addition, certain domain naming conventions must be followed.
As a result, SCOM does not exist without AD DS.
https://learn.microsoft.com/en-us/system-center/scom/system-requirements?view=sc-om-2019
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