A physical disk represents the entire disk and points to the following:

\Device\Harddiskx\Partition0

Symbolic link name \\.\PhysicalDrivex is automatically defined by Windows for every hard disk in the computer. For example, a computer with three hard disks have the following symbolic links:

\\.\PhysicalDrive0 
\\.\PhysicalDrive1 
\\.\PhysicalDrive2 

Internally, these names expand to the following:

\\.\PhysicalDrive0 =\Device\Harddisk0\Partition0 
\\.\PhysicalDrive1 =\Device\Harddisk1\Partition0 
\\.\PhysicalDrive2 =\Device\Harddisk2\Partition0 

Partition0 is special, because it represents the entire physical disk regardless of any partitioning scheme on that disk. Windows writes a signature on the first block of all disks it recognizes. To avoid overwriting that block, Oracle Database skips the first block of a physical raw partition that is used for an Oracle Database data file.