select
  sid,                                     -- SID NUMBER
  sess_serial#,                            -- SESS_SERIAL# NUMBER
  wait_id,                                 -- WAIT_ID NUMBER
  wait_event,                              -- WAIT_EVENT NUMBER
  wait_event_text,                         -- WAIT_EVENT_TEXT VARCHAR2(64)
  blocker_instance_id,                     -- BLOCKER_INSTANCE_ID NUMBER
  blocker_sid,                             -- BLOCKER_SID NUMBER
  blocker_sess_serial#                     -- BLOCKER_SESS_SERIAL# NUMBER
from
  gv$session_blockers
where
  inst_id = USERENV('Instance')