由于历史原因，应用升级需要成本，最近新上了一套oracle 10g RAC （10.2.0.5），测试时，从其他应用服务器，链接这套数据库，使用的是vip链接，发现大量报错，报错为ora-12545因目标主机或对象不存在。
ORA-12545: Connect Failed because target host or object does not exist
查询网上资料和mos文档，
导致这个问题的原因
Whe LOCAL_LISTENER is not set at all or is not set correctly, PMON can register both the VIP hostname and the physical hostname with the REMOTE_LISTENER. This is incorrect in RAC but if it does occur, the client can intermittently be routed to a listener endpoint on either of these addresses. If the client is unable to resolve the physical hostname or even the vip hostname, the connection will fail with ORA-12545.
由于LOCAL_LISTENER未配置或者配置不争取，PMON进程使用的是REMOTE_LISTENER注册vip hostname和物理地址，在rac里面，这是不对的配置，客户端无法使用这些地址正确路由到监听服务器。如果客户端无法正确解析物理地址或者vip的hostname，链接就会报 ORA-12545错误。
Additionall, if the VIP hostname cannot be resolved, but the VIP numerical address is reachable; then this VIP numerical address should be used as the HOST value for LOCAL_LISTENER instead.
And important first set is to check the output for : lsnrctl services
You should not see the physical hostname in the handler information for your RAC instances. Here's an example of an incorrect lsnrctl services output for a 2-node RAC cluster:
lsnrctl services oracle_rac_listener
Service "oracle.oracle.com" has 2 instance(s).
Instance "orcl1", status READY, has 2 handler(s) for this service...
Handler(s):
"DEDICATED" established:0 refused:0 state:ready
Remote Server
(ADDRESS=(PROTOCOL=TCP)(HOST=myphysicalhost1)(PORT=1521))
"DEDICATED" established:326 refused:0 state:ready
LOCAL SERVER
Instance "orcl2", status READY, has 1 handler(s) for this service...
Handler(s):
"DEDICATED" established:394371 refused:0 state:ready
Remote Server
(ADDRESS=(PROTOCOL=TCP)(HOST=myphysicalhost2)(PORT=1521))
Here's an example of what it ought to look like when LOCAL_LISTENER is configured correctly:
lsnrctl services oracle_rac_listener
Service "oracle.oracle.com" has 2 instance(s).
Instance "orcl1", status READY, has 2 handler(s) for this service...
Handler(s):
"DEDICATED" established:0 refused:0 state:ready
Remote Server
(ADDRESS=(PROTOCOL=TCP)(HOST=myVIP_host1)(PORT=1521))
"DEDICATED" established:326 refused:0 state:ready
LOCAL SERVER
Instance "orcl2", status READY, has 1 handler(s) for this service...
Handler(s):
"DEDICATED" established:394371 refused:0 state:ready
Remote Server
(ADDRESS=(PROTOCOL=TCP)(HOST=myVIP_host2)(PORT=1521))
解决方案：
分别修改两边的RAC实例的LOCAL_LISTENER配置。
alter system set LOCAL_LISTENER="(address=(protocol=tcp)(port=1521)(host=))" scope=both sid='INSTANCE_NAME1';
alter system set LOCAL_LISTENER="(address=(protocol=tcp)(port=1521)(host=))" scope=both sid='INSTANCE_NAME2';
另外，相关配置REMOTE_LISTENER.
alter system set REMOTE_LISTENER='' scope=both sid='*';
另外parallel_instance_group参数也可以配置不一样的值
alter system set parallel_instance_group="A" scope=both sid='INSTANCE_NAME1';
alter system set parallel_instance_group="B" scope=both sid='INSTANCE_NAME2';
最后，注意的是，修改完后，重启监听，如果重启监听都不行，重启一下数据库或者两个实例重启一下。
