ORA-01221: data file [string] is not the same file to a background process
Cause: When the database writer opens the data file, it is accessing a different physical file than the foreground doing the recovery. The timestamp set in the file header by the foreground was not found by the background. It may be that the background process could not read the file at all.
Action: Look in the DBWR trace file for the error it recieved when attempting to read the file header. Reconfigure the operating system as needed to have the file name successfully access the same file when opened by a background process.