Query to find DB_LINK in an Oracle instance

 SELECT obj.object_type         "Object Type",
       obj.owner               "Object Owner",
       obj.object_name         "Object Name",
       obj.status              "Object Status",
       dbl.db_link             "DB Link",
       dbl.username            "DB Link",
       dbl.host                "DB Host"
  FROM dba_objects  obj,
       dba_db_links dbl
 WHERE obj.object_name = dbl.db_link
   AND obj.object_type = 'DATABASE LINK';