In a process to restore a data volume in a first memory, a virtual
point-in-time (PIT) copy of the data volume is created. Creating the
virtual PIT copy includes creating first, second and third maps in
memory. Each of the first, second, and third maps includes a plurality of
multi-bit entries. Each of the entries of the first and second maps
corresponds to a respective memory region of the first memory, while each
of the entries of the third map corresponds to a respective memory region
of a second memory for storing data of the virtual PIT copy.