MSDN:
hFile
[in] Handle to the file from which to create a mapping object. The file must be opened with an access mode compatible with the protection flags specified by the flProtect parameter. It is recommended, though not required, that files you intend to map be opened for exclusive access.
If hFile is INVALID_HANDLE_VALUE, the calling process must also specify a mapping object size in the dwMaximumSizeHigh and dwMaximumSizeLow parameters. In this case, CreateFileMapping creates a file-mapping object of the specified size backed by the operating-system paging file rather than by a named file in the file system. The file-mapping object can be shared through duplication, through inheritance, or by name. The initial contents of the pages in the file-mapping object are zero.