It's there:
Home > Support > Technical Documentation and Advisories > Software ~ A-B ~ Documentation > Avamar > Avamar Data Store > Gen3

I found some docs here:

https://powerlink.emc.com/nsepn/webapps/btg548664833igtcuup4826/km/appmanager/km/secureDesktop?_nfpb=true&_pageLabel=default&internalId=0b014066804771e4&_irrt=true

But was expecting to see them in the Avmar support web page.