--查当前正在运行的事务以及sql
SELECT t.start_date,
t.start_scn,
s.sid,
s.serial#,
s.username,
s.program,
q.sql_text,
q.sql_id
FROM v$transaction t
left join v$session s
on s.taddr = t.addr
left join (select sql_id, sql_text, hash_value
from v$sql
group by sql_id, hash_value, sql_text) q
on q.hash_value = s.prev_hash_value
order by t.start_date, s.username;

我觉得，大事务是指运行时间很长的事务。不知道你怎么看？