Multiple Domains for Forms and Reports s/w stack??

 Hi,

I am looking for confirmation that I am installing my s/w stack correctly.

As I have installed it, WLS created a base_domain.  

Then OAM created another domain.

Then F&R created yet another one. (Per the documentation).  Also per https://blogs.oracle.com/olaf/entry/ofm_11g_implementing_oam_sso_w, with is a tiny bit dated, F&R must have its own domain.

Is it common to have multiple domains like this?  I have had a picture in my head (and all the documentation) of a single domain with multiple managed servers, but it looks like I will wind up with 3-4 domains.