Where CUA exists?

Hello Folks,

Let us say we got R3 systems configured with ITS administration.

Now, if i have CUA configured on these R3 systems,then does it mean

1.CUA resides with in (One of the )R3 system?

2.Or else, with in Workplace Server (WP)system?

Also, does WP needs its own database to store the meta data?

Thank you for your time.

Ram