转 [分享一个SQL] 查会话阻塞关系，层次关系.

with ash as (select /*+ materialize*/* from DBA_HIST_ACTIVE_SESS_HISTORY  where sample_time between timestamp '2015-03-18 15:00:00' and timestamp



'2015-03-18 15:01:00'), 

   chains as ( 

   select session_id, level lvl, 

          sys_connect_by_path(sql_id,
' -> ') path, 

          connect_by_isleaf
isleaf 

     from ash

    start with event = 'row
cache lock' 

    connect by nocycle (prior blocking_session
= session_id and prior blocking_session_serial# = session_serial#
and prior sample_id = sample_id)) 

 select lpad(round(ratio_to_report(count(*)) over () * 100)||'%',5,' ')
"%This", 

        count(*) samples, 

        path 

   from chains 

  where isleaf = 1 

  group by path 

  order by samples