描述：
刚搭建起来的rac环境，通过监听连接：sqlplus system/oracle@11grac 发现报了如下错误：
ORA-12545: 因目标主机或对象不存在, 连接失败
查看两个节点的tnsnames.ora 信息如下：
11grac =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = rac-scan)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = test)
)
)
分别在两个节点查看参数文件信息：
rac1：
SQL> show parameter listener
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
listener_networks string
local_listener string (DESCRIPTION=(ADDRESS_LIST=(AD
DRESS=(PROTOCOL=TCP)(HOST=rac1
-vip)(PORT=1521))))
remote_listener string rac-scan:1521
rac2：
SQL> show parameter listener
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
listener_networks string
local_listener string (DESCRIPTION=(ADDRESS_LIST=(AD
DRESS=(PROTOCOL=TCP)(HOST=rac2
-vip)(PORT=1521))))
remote_listener string rac-scan:1521
看到以上信息后，肯定第一步确定了我现在系统的hosts文件，确保rac-scan对应的ip地址存在。
然后尝试tnsping 11grac，发现可以通。因为tnsping只检查IP地址和端口是否能连通，至于数据库实例状态，监听注册了哪些服务这些，它是不检查的.
查看SCAN Listener 的状态：
[grid@rac1 admin]$ lsnrctl status LISTENER_SCAN1
LSNRCTL for Linux: Version 11.2.0.1.0 - Production on 24-OCT-2014 11:00:04
Copyright (c) 1991, 2009, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN1)))
STATUS of the LISTENER
------------------------
Alias LISTENER_SCAN1
Version TNSLSNR for Linux: Version 11.2.0.1.0 - Production
Start Date 24-OCT-2014 10:51:50
Uptime 0 days 0 hr. 8 min. 13 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /u01/app/11.2.0/grid/network/admin/listener.ora
Listener Log File /u01/app/11.2.0/grid/log/diag/tnslsnr/rac1/listener_scan1/alert/log.xml
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=LISTENER_SCAN1)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.15.120)(PORT=1521)))
Services Summary...
Service "test" has 2 instance(s).
Instance "test1", status READY, has 1 handler(s) for this service...
Instance "test2", status READY, has 1 handler(s) for this service...
Service "testXDB" has 2 instance(s).
Instance "test1", status READY, has 1 handler(s) for this service...
Instance "test2", status READY, has 1 handler(s) for this service...
The command completed successfully
以上看来，是正常状态。
[grid@rac1 admin]$ lsnrctl service LISTENER_SCAN1
LSNRCTL for Linux: Version 11.2.0.1.0 - Production on 24-OCT-2014 11:03:53
Copyright (c) 1991, 2009, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN1)))
Services Summary...
Service "test" has 2 instance(s).
Instance "test1", status READY, has 1 handler(s) for this service...
Handler(s):
"DEDICATED" established:0 refused:0 state:ready
REMOTE SERVER
(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=rac1-vip)(PORT=1521)))
Instance "test2", status READY, has 1 handler(s) for this service...
Handler(s):
"DEDICATED" established:0 refused:0 state:ready
REMOTE SERVER
(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=rac2-vip)(PORT=1521)))
Service "testXDB" has 2 instance(s).
Instance "test1", status READY, has 1 handler(s) for this service...
Handler(s):
"D000" established:0 refused:0 current:0 max:1022 state:ready
DISPATCHER <machine: rac1.lyg.com, pid: 5968>
(ADDRESS=(PROTOCOL=tcp)(HOST=rac1.lyg.com)(PORT=26672))
Instance "test2", status READY, has 1 handler(s) for this service...
Handler(s):
"D000" established:0 refused:0 current:0 max:1022 state:ready
DISPATCHER <machine: rac2.lyg.com, pid: 6006>
(ADDRESS=(PROTOCOL=tcp)(HOST=rac2.lyg.com)(PORT=54390))
The command completed successfully
以上状态，正常。
手工尝试关闭rac2节点的监听：
[grid@rac2 ~]$ lsnrctl stop
LSNRCTL for Linux: Version 11.2.0.1.0 - Production on 24-OCT-2014 11:09:42
Copyright (c) 1991, 2009, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER)))
The command completed successfully
[grid@rac2 ~]$ lsnrctl status
LSNRCTL for Linux: Version 11.2.0.1.0 - Production on 24-OCT-2014 11:09:49
Copyright (c) 1991, 2009, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER)))
TNS-12541: TNS:no listener
TNS-12560: TNS:protocol adapter error
TNS-00511: No listener
Linux Error: 2: No such file or directory
[grid@rac2 ~]$ crs_stat -t
Name Type Target State Host
------------------------------------------------------------
ora.DATA.dg ora....up.type ONLINE ONLINE rac1
ora.FRA.dg ora....up.type ONLINE ONLINE rac1
ora....ER.lsnr ora....er.type ONLINE ONLINE rac1
ora....N1.lsnr ora....er.type ONLINE ONLINE rac1
ora....VOTE.dg ora....up.type ONLINE ONLINE rac1
ora.asm ora.asm.type ONLINE ONLINE rac1
ora.eons ora.eons.type ONLINE ONLINE rac1
ora.gsd ora.gsd.type OFFLINE OFFLINE
ora....network ora....rk.type ONLINE ONLINE rac1
ora.oc4j ora.oc4j.type OFFLINE OFFLINE
ora.ons ora.ons.type ONLINE ONLINE rac1
ora....SM1.asm application ONLINE ONLINE rac1
ora....C1.lsnr application ONLINE ONLINE rac1
ora.rac1.gsd application OFFLINE OFFLINE
ora.rac1.ons application ONLINE ONLINE rac1
ora.rac1.vip ora....t1.type ONLINE ONLINE rac1
ora....SM2.asm application ONLINE ONLINE rac2
ora....C2.lsnr application OFFLINE OFFLINE
ora.rac2.gsd application OFFLINE OFFLINE
ora.rac2.ons application ONLINE ONLINE rac2
ora.rac2.vip ora....t1.type ONLINE ONLINE rac2
ora....ry.acfs ora....fs.type ONLINE ONLINE rac1
ora.scan1.vip ora....ip.type ONLINE ONLINE rac1
ora.test.db ora....se.type ONLINE ONLINE rac1
此时，可以看到rac2节点的监听服务已经关闭了。再次查看SCAN Listener的状态：
[grid@rac1 admin]$ lsnrctl service LISTENER_SCAN1
LSNRCTL for Linux: Version 11.2.0.1.0 - Production on 24-OCT-2014 11:16:28
Copyright (c) 1991, 2009, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=LISTENER_SCAN1)))
Services Summary...
Service "test" has 2 instance(s).
Instance "test1", status READY, has 1 handler(s) for this service...
Handler(s):
"DEDICATED" established:0 refused:0 state:ready
REMOTE SERVER
(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=rac1-vip)(PORT=1521)))
Instance "test2", status READY, has 1 handler(s) for this service...
Handler(s):
"DEDICATED" established:0 refused:0 state:blocked
REMOTE SERVER
(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=rac2-vip)(PORT=1521)))
Service "testXDB" has 2 instance(s).
Instance "test1", status READY, has 1 handler(s) for this service...
Handler(s):
"D000" established:0 refused:0 current:0 max:1022 state:ready
DISPATCHER <machine: rac1.lyg.com, pid: 5968>
(ADDRESS=(PROTOCOL=tcp)(HOST=rac1.lyg.com)(PORT=26672))
Instance "test2", status READY, has 1 handler(s) for this service...
Handler(s):
"D000" established:0 refused:0 current:0 max:1022 state:ready
DISPATCHER <machine: rac2.lyg.com, pid: 6006>
(ADDRESS=(PROTOCOL=tcp)(HOST=rac2.lyg.com)(PORT=54390))
The command completed successfully
可以看到此时的rac2节点的监听已经是blocked状态。此时，我们再尝试从rac2节点上去连接看看：
[oracle@rac2 ~]$ sqlplus system/oracle@TEST
SQL*Plus: Release 11.2.0.1.0 Production on Fri Oct 24 11:18:35 2014
Copyright (c) 1982, 2009, Oracle. All rights reserved.
ERROR:
ORA-28002: the password will expire within 6 days
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
With the Partitioning, Real Application Clusters, Automatic Storage Management, OLAP,
Data Mining and Real Application Testing options
SQL> show parameter instance_name;
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
instance_name string test1
可以看到，此时连接，已经体现了rac的故障切换功能。自动的连接到了实例1上。。。
原因是由于 Oracle会把local_listener注册到remote_listener(66/69)上，由于没有设置local_listener,默认就是"(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=hostname)(PORT=1521)))"
当client尝试连接66/69时，有一定机会返回 "(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=hostname)(PORT=1521)))"给client ，让client转向,而client不认识 HOST=hostname，造成 12545