Oracle Error Message
ORA-19941: invalid blocksize in cross platform datafile string
Reason for the Error
Blocksize in header of datafile copy being converted at target was invalid. Either datafile has not been made read/write with compatibility 10.0 or greater at source database or datafile copy is corrupted.
Solution
Make a new datafile copy taken after tablespace has been made read/write with compatibility 10.0 at source database and retry conversion.