Data Pump legacy mode requires that you review and update your existing scripts written for original Export and Import because of differences in file format and error reporting.
Data Pump Export and Import do not generate log files in the same format as those created by original Export and Import. Any scripts you have that parse the output of original Export and Import must be updated to handle the log file format used by Data Pump Export and Import. For example, the message
Successfully Terminated does not appear in Data Pump log files.
Data Pump Export and Import may not produce the same errors as those generated by original Export and Import. For example, if a parameter that is ignored by Data Pump Export would have had an out-of-range value in original Export, then an informational message is written to the log file stating that the parameter is being ignored. No value checking is performed, therefore no error message is generated.