If you have access to the Oracle DB server OS and user (e.g. via ssh or telnet), then you don’t need to have credentials for any DB user to be able to run the data pump commands, all you have to do is adding userid=”‘/ as sysdba'”

e.g.

expdp userid=”‘/ as sysdba'” schemas=x,y,z directory=datapump_output_dir dumpfile=data_pump_output_.dmp logfile=data_pump_output.log