truncate table output
/

/*****************************************************************************
/* Using the DBMS_OUTPUT package
/* DBMS_OUTPUT.put_line() to add a line to the DBMS_OUTPUT buffer
/* DBMS_OUTPUT.get_line() to retrieve a line from the DBMS_OUTPUT buffer
/*****************************************************************************/

BEGIN
    DBMS_OUTPUT.put_line('Hello World');
END;
/

DECLARE
    line   varchar2(100);
    status integer;
    x 	   integer;
BEGIN
    DBMS_OUTPUT.put_line('Hello World 1');		-- pint to the buffer
    DBMS_OUTPUT.get_line(line, status);			-- status 0=OK, 1=end.  Buffer is cleared
    insert into output values(line);			-- line will have Hello World 1
--
    DBMS_OUTPUT.put('Hello World 2, ');			-- no new line character
    DBMS_OUTPUT.put_line('Goodbye World');	
    x :=power(2, 8);
    DBMS_OUTPUT.put_line('2 to the 8 is: ' || x );
END;
/

select * from output