Overhead for turning on the user reporting

We are in an AD environment owned by our parent company. They have placed domain controllers in our physical location and all workstations are joined to that domain. I have Desktop Central set up, and agents deployed to the PCs in our organization and would like to utilize the User Logon reports, however Desktop Central does not have the ability to restrict its scanning of AD to our organization's OU.

If I was to turn on the User Logon reporting, what does Desktop Central do to get that information? Does it just query the agents, the local domain controller, or will it start querying the entire AD forest? I wanted to understand the scope of it getting this information as I don't want it to be intrusive or resource intensive.

Thanks,
Dave