some queryes to measure disk io

 select 100*(round ( count (*)/sum(count(*)) over(),2 )) as pct ,nvl(wait_class,'CPU') wait_class from v$active_session_history group by wait_class order by 1 desc;
 select 100*(round ( count (*)/sum(count(*)) over(),2 )) as pct ,nvl(event,'CPU') event from v$active_session_history where wait_class like '%I/O%' group by event order by 1 desc; 

generate pivot list

 select listagg( ''''||event||'''',',') within group (order by event )from v$active_session_history where wait_class like '%I/O%' group by event ;

or top wait pivot list:

with disk_events as  (
  select 100*(round ( count (*)/sum(count(*)) over(),2 )) as pct ,nvl(event,'CPU') event from v$active_session_history where wait_class like '%I/O%' group by event )
 select listagg( ''''||event||'''',',') within group (order by event )from disk_events where pct >5 ;

query and result

new:select * from
(select event,case when est_waits >0  
      then  round (est_dbtime_ms / est_waits,1)
              
                else null
                end
  as est_avg_latency_ms,
    time#
from ( 
      select event,
        round(
              sum(
                    case when time_waited >0 
                    then greatest(1,1000000/time_waited) 
                            else 0 end )
            ) as est_waits,
      sum(1000) as est_dbtime_ms ,
 TRUNC( ash.SAMPLE_TIME, 'MI') - mod( EXTRACT(minute FROM  ash.SAMPLE_TIME), 5) /(24 * 60) time#
from v$active_session_history ash 
  where ash.wait_class ='User I/O' 
      group by TRUNC(SAMPLE_TIME, 'MI') - mod( EXTRACT(minute FROM SAMPLE_TIME), 5) /(24 * 60) ,event 
      )    )
 pivot ( sum(est_avg_latency_ms) for event in (
 'db file scattered read','db file sequential read','log file parallel write')
 ) order by time#

TIME#               |                'db file scattered read' |               'db file sequential read' |               'log file parallel write'
------------------- | --------------------------------------- | --------------------------------------- | ---------------------------------------
10.08.2015 14.10.00 |                                     2,2 |                                      ,3 |                                  <NULL>
10.08.2015 14.15.00 |                                     2,4 |                                      ,2 |                                  <NULL>
10.08.2015 14.20.00 |                                     1,7 |                                      ,3 |                                  <NULL>
10.08.2015 14.25.00 |                                     1,3 |                                      ,3 |                                  <NULL>
10.08.2015 14.30.00 |                                     3,5 |                                      ,2 |                                  <NULL>
10.08.2015 14.35.00 |                                     1,8 |                                      ,3 |                                  <NULL>
10.08.2015 14.40.00 |                                     1,1 |                                      ,3 |                                  <NULL>
10.08.2015 14.45.00 |                                     2,6 |                                      ,2 |                                  <NULL>
10.08.2015 14.50.00 |                                     1,5 |                                      ,3 |                                  <NULL>
10.08.2015 14.55.00 |                                     1,2 |                                      ,3 |                                  <NULL>
10.08.2015 15.00.00 |                                     2,6 |                                      ,2 |                                  <NULL>
10.08.2015 15.05.00 |                                     1,3 |                                      ,4 |                                  <NULL>
10.08.2015 15.10.00 |                                     1,6 |                                      ,3 |                                  <NULL>
10.08.2015 15.15.00 |                                       3 |                                      ,2 |                                  <NULL>
10.08.2015 15.20.00 |                                     1,4 |                                      ,3 |                                  <NULL>
10.08.2015 15.25.00 |                                     1,6 |                                      ,3 |                                  <NULL>
10.08.2015 15.30.00 |                                     3,1 |                                      ,2 |                                  <NULL>
10.08.2015 15.35.00 |                                     1,8 |                                      ,4 |                                  <NULL>
10.08.2015 15.40.00 |                                     1,2 |                                      ,3 |                                  <NULL>
10.08.2015 15.45.00 |                                     2,5 |                                      ,2 |                                  <NULL>
10.08.2015 15.50.00 |                                     1,6 |                                      ,3 |                                  <NULL>
10.08.2015 15.55.00 |                                     1,4 |                                      ,3 |                                  <NULL>
10.08.2015 16.00.00 |                                     4,8 |                                      ,2 |                                  <NULL>
10.08.2015 16.05.00 |                                     1,8 |                                      ,4 |                                  <NULL>
10.08.2015 16.10.00 |                                     1,2 |                                      ,4 |                                  <NULL>
10.08.2015 16.15.00 |                                       3 |                                      ,2 |                                  <NULL>
10.08.2015 16.20.00 |                                     1,3 |                                      ,3 |                                  <NULL>
10.08.2015 16.25.00 |                                     1,1 |                                      ,3 |                                  <NULL>
10.08.2015 16.30.00 |                                     3,1 |                                      ,2 |                                  <NULL>
10.08.2015 16.35.00 |                                     1,6 |                                      ,3 |                                  <NULL>
10.08.2015 16.40.00 |                                     1,6 |                                      ,3 |                                  <NULL>
10.08.2015 16.45.00 |                                     2,9 |                                      ,2 |                                  <NULL>
10.08.2015 16.50.00 |                                     1,6 |                                      ,3 |                                  <NULL>
10.08.2015 16.55.00 |                                     1,3 |                                      ,2 |                                  <NULL>
10.08.2015 17.00.00 |                                     2,2 |                                      ,2 |                                  <NULL>
10.08.2015 17.05.00 |                                     1,5 |                                      ,4 |                                  <NULL>
10.08.2015 17.10.00 |                                     1,7 |                                      ,3 |                                  <NULL>
10.08.2015 17.15.00 |                                       3 |                                      ,2 |                                  <NULL>
10.08.2015 17.20.00 |                                     1,8 |                                      ,3 |                                  <NULL>
10.08.2015 17.25.00 |                                     1,3 |                                      ,3 |                                  <NULL>
10.08.2015 17.30.00 |                                     3,3 |                                      ,3 |                                  <NULL>
10.08.2015 17.35.00 |                                     1,6 |                                      ,3 |                                  <NULL>
10.08.2015 17.40.00 |                                      ,7 |                                      ,3 |                                  <NULL>

this output can be used to build graphs: