"data file header is media corrupt"
*Cause: The file header block is internally inconsistent. The beginning
of the block has a header with a checksum and other data for
insuring the consistancy of the block. It is possible that
the last disk write did not operate correctly. The most likely
problem is that this is not a datafile for any database.
*Action: Have operating system make correct file available to database.
If the trace file dump indicates that only the checksum is wrong,
restore from a backup and do media recovery.