In reply to sunils:
There is no uvm_reg_pkg.sv in the UVM base class library. You get all of the UVM reg functionality when you import uvm_pkg::*;. And you get all UVM macros when you `include "uvm_macros.svh"
Since the OVM had no similar functionality, the uvm_reg_pkg was an additional package for OVM users to get access to the UVM register package when they were not ready to fully migrate to the UVM.