Oracle Solution for Error ora-01205

ORA-01205: not a data file - type number in header is string

What triggered the Error:

The file type in the header is not correct for a data file. This is probably a log file or control file. If the type is not a small non-zero positive number then the header is corrupted.

What should we do to fix it:

Restore a copy of the correct data file and do recovery as needed.