create table comment_table
(
   comment_text varchar2(255)
 , event_date date
)
/

create or replace procedure comment_procedure (comment_text_p in varchar2)
as
  pragma autonomous_transaction;
begin
   insert into comment_table (comment_text,event_date) values (comment_text_p,sysdate);
   commit;
end;
/
show errors

begin
--
-- capture start time
--
   comment_procedure('test1 start');

--
-- do some stuff
--
   dbms_lock.sleep(3);

--
-- capture the end time
--
   comment_procedure('test1 end');
end;
/

commit;

alter session set nls_Date_format = 'dd-mon-rrrr hh24:mi:ss';

col comment_text format a20

select * from comment_table;
 
select  substr(comment_text,1,instr(comment_text,' ')-1) event_name
      , round(
               (
                  select (b.event_date-a.event_date)*24*60*60
                  from comment_table b
                  where substr(a.comment_text,1,instr(a.comment_text,' '))||'end' = b.comment_text
               )
             ) seconds
from comment_table a
where comment_text like '%start'
order by event_date
/

commit;