sqlldr userid=<username>/<password>@<database_connection>
control=<path>/<ctl_file_name> log=<path>/<log_file_name>

Example-

sqlldr userid=username/password@hostname/
control = 'D:\Field_value_key\Field_value_key.ctl' 
log='D:\Field_value_key\Field_value_key.log'