VPLEX Licensing Model

Hi, 

I have question about licensing model of VPLEX,

I want to have a METRO VPLEX package with 3 storages in each site and 120TB capacity license.

So, VPLEX how calculates capacity consumption in each site for LOCAL and METRO used capacity?
Is it "Array-Based" or "120TB for LOCAL & 120TB for METRO" or "shared 120TB capacity on each cluster for METRO&LOCAL" or something else?

Is there any documents for reference about licensing model and calculations behavior?

Thank you in advance.

Regards