Does your physical server currently connects to the storage using a ISCSI HBA or ISCSI S/W initiator?
When you use RDM to connect an existing LUN which was earlier mapped on a physical host it does not require any additional step as the file system is already created on the LUN and the OS has to just mount the LUN now; not sure if you have to preform any additional tasks if you are running Oracle RAC on the server.