为了避免传说中的RAC风暴，还是将各个集群节点列出来比较合适

xman= (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.19.150)(PORT = 1521)) (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.19.151)(PORT = 1521)) (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.19.153)(PORT = 1521)) ) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = xman) ) )