Oracle demonstrates only a "successful completed PL / SQL procedure." Lack of output after code execution

Question

This is what he shows. There is no way out even after running the code

    SQL> DECLARE
    2     message  varchar2(20):= 'Hello, World!';
    3  BEGIN
    4     dbms_output.put_line(message);
    5  END;
    6  /

    PL/SQL procedure successfully completed.

Answer 1

Try the following:

set serveroutput on;

DECLARE
   message  varchar2(20):= 'Hello, World!';
BEGIN
   dbms_output.put_line(message);
END;
/