Total cursors open
select sum(a.value) from v$sesstat a, v$statname b, v$session s where a.statistic# = b.statistic# and s.sid=a.sid and b.name = 'opened cursors current' /
Total open cursors, by session
select a.value, s.username, s.sid, s.serial# from v$sesstat a, v$statname b, v$session s where a.statistic# = b.statistic# and s.sid=a.sid and b.name = 'opened cursors current' /