Description of Pentaho BA Databases

I am using Pentaho 5.x and I'm trying to find out what the BA Server uses the Hibernate and Jackrabbit databases for. I know that in 4.8, Hibernate was used to store user data and links to custom reports which were store on the file system. There was no Jackrabbit in 4.8.

In 5.x, I'm assuming that Jackrabbit now stores the user data and reports? If so, then what is Hibernate being used for?

Thanks