migraton from hypervisor6 to hypervisor7

Hi,
We are considering migration ll out machines to RHEL 7, including the hypervisors. At the moment out RHEV-M is running on separate server outside cloud.

We have 3 hypervisors (with more than 100 VMs) running latest hypervisor6, and I was wondering if there is any documentation about migrating hypervisors from version 6 to 7 without loosing data and configured VMs.

Can I just Delete machine from cluster, reinstall with hypervisor7 and add it back to cluster? Will I be able to migrate machines running on hypervisor6 to hypervisor7?

Thanks,
Krzysztof