set serveroutput on is necessary to see the output that was written with dbms_output set serverout[put] {on | off} [size {n | unl[imited]}] [for[mat] {wra[pped] | wor[d_wrapped] | tru[ncated]}]
outon.sql is a most simple SQL script to be put into a $SQLPATH directory. It «enables» dbms_output in SQL*Plus. set variables