DBMS_OUTPUT is a PL/SQL package that can be used to print or write output from a PL/SQL program to a buffer (or the screen).
Note that the output buffer is not released until the PL/SQL block completes. So, you can only see the output after execution - and not as the program executes.
Enable dbms_output support.
Deactivate dbms_output support - put, put_line, new_line commands have no effect.
Insert text into the output buffer.
Insert a line (text with end of line symbol) into the output buffer.
Insert end of line symbol into output buffer.
Read one line from the buffer.
Read line array from the buffer.
SET SERVEROUTPUT ON BEGIN dbms_output.put_line('Output from PL/SQL...'); END; /