This should work with oracle 8 and +
The consistent=yes parameter locks the Objects as read only to ensure data consistency.
Depending on the environment settings the @oracle_sid parameter in the user name may be optional.
exp User_name/user_pass@oracle_sid FULL=y FILE=my_export_file.dmp LOG=my_export_log CONSISTENT=y
or
exp userid=User_name/user_pass@Oracle_sid FULL=y FILE=my_export_file.dmp LOG=my_export_log CONSISTENT=y
to export schema from a user (owner_name) while logged as an admin (dba_name)
exp userid=dba_name/dba_pass FULL=y FILE=my_export_file.dmp LOG=my_export_log CONSISTENT=y owner=owner_name