Oracle: V$DBLINK

select
  dbl.protocol,
  dbl.db_link,
  dbl.logged_on,
  dbl.heterogeneous,
  usr.username,
  dbl.open_cursors,
  dbl.in_transaction,
  dbl.update_sent,
  dbl.commit_point_strength
from
  v$dblink  dbl                                left join
  dba_users usr on dbl.owner_id = usr.user_id;

select
   username,
   osuser,
   status,
   sid,
   serial#,
   machine,
   process,
   terminal,
   program
from
   v$session
where
   saddr in (select k2gtdses from sys.x$k2gte);