invalid or corrupt media format

  Explanation:  The media or disk file is in an invalid format.

  User  Action:   This  message  indicates  a  media  or  hardware
  problem.   Check  the  system error log and consult the hardware
  support group for further information.  Reinstalling Oracle  Rdb
  will  resolve  the  problem.   However,  if  the error regularly
  occurs, faulty hardware is almost certainly the cause.