Create Explain Plan Automatically

create or replace
function createplan
(
  sql_text in varchar2
)
return varchar2
as
     plan_stmt_id_ varchar2(4000);
begin
  select to_char(plan_stmt_id.nextval) into plan_stmt_id_ from dual;
  execute immediate  ( 'EXPLAIN PLAN SET STATEMENT_ID = '''||plan_stmt_id_||''' INTO plan_table FOR '||sql_text);
  return plan_stmt_id_;
end createplan;

Calculate top 10 database wait events per wait class

select * from (
select c.wait_class as wait_class,e.event as event
from V$system_event e ,V$SYSTEM_WAIT_CLASS c
where e.wait_class_id=c.wait_class_id
order by e.total_waits desc
) tab
where rownum <=10