症状：telnet vip 1521连不行，telnet nodea却可以
分析：估计是监听的问题
(ADDRESS = (PROTOCOL = TCP)(HOST = nodea)(PORT = 1521))
原先hosts里配了nodea对应的ip，主机名也是nodea，这就造成只监听这个ip
改成这样就可以了
(ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))
(ADDRESS = (PROTOCOL = TCP)(HOST = nodea)(PORT = 1521))
(ADDRESS = (PROTOCOL = TCP)(HOST = vip)(PORT = 1521))
