Domain - Local security Database

[beaumontdvd]

Hi all, am I right in saying that in a workgroup each computer has its own local security database and in a domain the local security database isn't held on the DC for security? If not where is it held?

Also that you cannot logon to a domain locally? So when you login you will be logging in using domain credentials based on the active directory entries?

Also what happens if the domains down and AD is not installed would you be able to login to the dc?


Hope someone can explain in the simplest terms as I'm new to this domain environment

thanks,
Dave