How to deploy IDM, RHDS vs RH IdM

Hi
I am looking for some resources about how deploy RedHat IDM we have RHEL subscription, do we need any other subscription for RH IDM ?

We are currently using openLDAP can anyone confirm me how difficult it is to migrate from openLDAP to IdM?

lastly what are the major differences between Red Hat Directory Service and Red Hat IDM ?

thanks