"corrupt redo log block header"
*Cause: The block header on the redo block indicated by the accompanying
error, is not reasonable.
*Action: Do recovery with a good version of the log or do time based
recovery up to the indicated time. If this happens when archiving,
archiving of the problem log can be skipped by clearing the log
with the UNARCHIVED option. This must be followed by a backup of
every datafile to insure recoverability of the database.