"log %s of thread %s is needed for recovery of offline datafiles"
*Cause: Log cannot be cleared because the redo in it is needed to recover
offline datafiles. It has not been archived so there is no
other copy available. If the log is cleared the tablespaces
containing the files will have to be dropped.
*Action: Archive the log then repeat the clear command. If archiving is not
possible, and dropping the tablespaces is acceptible, then add the
clause UNRECOVERABLE DATAFILE at the end of the clear command.