什么是tnsping?
可以参考官方文档的具体介绍
http://docs.oracle.com/cd/E11882_01/network.112/e41945/connect.htm#NETAG378
tnsping 实际上就是一个小工具，用来决定是否一个Oracle Net 网络服务（service）可以被接受。
从某种意义上来说，tnsping 针对的 sqlnet连接，就好比为我们常用的ping 命令来检查IP，主机名网络连接情况。
我们来做一个有趣的试验：
先来看看以下配置信息:
数据库所在服务器端：
数据库安装到Linux服务器，hostname = ttdev, IP 地址= 192.168.56.11, ORACLE_SID=ORCL
------
[oracle@ttdev ~]$ cat /home/oracle/app/oracle/product/11.2.0/dbhome_2/network/admin/listener.ora
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.56.11)(PORT = 1521))
)
)
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(PROGRAM = extproc)
(SID_NAME = PLSExtProc)
(ORACLE_HOME = /home/oracle/app/oracle/product/11.2.0/dbhome_2)
)
)
ADR_BASE_LISTENER = /home/oracle/app/oracle/
------
客户端：
在Windows ，安装oracle 客户端后，配置Windows 环境变量 TNS_ADMIN 指向 C:\app\liyang\product\11.2.0\client_2\network\admin
在该路径下，添加 tnsnames.ora 文件
------
TTORCL =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.56.11)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = orcl)
)
)
------
客户端的sqlnet.ora 使用默认
SQLNET.AUTHENTICATION_SERVICES = (NTS)
=============
试验一：
首先，我们来看一下数据库服务器端的实际情况：
通过putty 登录到Linux系统的oracle 用户，停掉数据库，并检查监听情况：
------
[oracle@ttdev ~]$ sqlplus / as sysdba
SQL*Plus: Release 11.1.0.7.0 - Production on Tue Mar 25 18:49:23 2014
Copyright (c) 1982, 2008, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> quit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
[oracle@ttdev ~]$ lsnrctl status
LSNRCTL for Linux: Version 11.2.0.2.0 - Production on 25-MAR-2014 18:52:03
Copyright (c) 1991, 2010, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.56.11)(PORT=1521)))
STATUS of the LISTENER
------------------------
Alias LISTENER
Version TNSLSNR for Linux: Version 11.2.0.2.0 - Production
Start Date 25-MAR-2014 18:14:27
Uptime 0 days 0 hr. 37 min. 36 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /home/oracle/app/oracle/product/11.2.0/dbhome_2/network/admin/listener.ora
Listener Log File /home/oracle/app/oracle/diag/tnslsnr/ttdev/listener/alert/log.xml
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.56.11)(PORT=1521)))
Services Summary...
Service "PLSExtProc" has 1 instance(s).
Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service... 《=========服务里面并没有ORCL，因为数据库刚刚被shutdown了！
The command completed successfully
------
在Windows 客户端， 开始 菜单=》 运行 =》 输入 cmd 命令，
进入dos 窗口，并输入 tnsping TTORCL, 返回
------
C:\Users\liyang>tnsping TTORCL
TNS Ping Utility for 64-bit Windows: Version 11.2.0.1.0 - Production on 26-3月 -
2014 10:06:08
Copyright (c) 1997, 2010, Oracle. All rights reserved.
已使用的参数文件:
C:\app\liyang\product\11.2.0\client_2\network\admin\sqlnet.ora
已使用 TNSNAMES 适配器来解析别名
尝试连接 (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = 192.1 《=====TNSPING 仍然解析成功，返回TTORCL的具体内容！
68.56.11)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = orcl)))
OK (20 毫秒)
------
上面返回的 “尝试连接” 后面部分是sqlnet 如何解析到的TTORCL 别名，或者叫 连接标识符。该别名的解析是通过客户端的 TNS_ADMIN指定路径下的 sqlnet.ora文件中的 NAMES.DIRECTORY_PATH 参数决定的。上面的试验结果显示的是通过 TNSNAMES 适配器 来解析成功的。
该请求可以看到，是通过 TCP 的网络协议 (PROTOCOL = TCP)， 连接到了 IP地址为 192.168.56.11 上的服务器（也可以是主机名），希望连接的端口为 1521, 服务名为 (SERVICE_NAME = orcl)。
连接20毫秒的意思是 一个预估的大概网络传输往返一次的时间。
以上测试说明了，不论数据库是否运行，只要监听存在并在运行，tnsping 都可以成功解析！
=============
试验二：
停止数据库实例，更改监听的端口为 1522 ， 启动监听：
------
[oracle@ttdev admin]$ sqlplus / as sysdba
SQL*Plus: Release 11.1.0.7.0 - Production on Tue Mar 25 21:07:28 2014
Copyright (c) 1982, 2008, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> quit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
[oracle@ttdev admin]$ ps -ef | grep smon
oracle 4335 3326 0 21:08 pts/1 00:00:00 grep smon
《====没有数据库实例进程运行
[oracle@ttdev admin]$ lsnrctl status
LSNRCTL for Linux: Version 11.2.0.2.0 - Production on 25-MAR-2014 21:08:00
Copyright (c) 1991, 2010, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.56.11)(PORT=1522)))
《====端口已经更改！
STATUS of the LISTENER
------------------------
Alias LISTENER
Version TNSLSNR for Linux: Version 11.2.0.2.0 - Production
Start Date 25-MAR-2014 21:01:31
Uptime 0 days 0 hr. 6 min. 29 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /home/oracle/app/oracle/product/11.2.0/dbhome_2/network/admin/listener.ora
Listener Log File /home/oracle/app/oracle/diag/tnslsnr/ttdev/listener/alert/log.xml
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.56.11)(PORT=1522))) 《======监听1522 正常运行
Services Summary...
Service "PLSExtProc" has 1 instance(s).
Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service... 《====没有监听到 ORCL的服务
The command completed successfully
------
接下来，回到客户端，执行 tnsping ttorcl
------
C:\Users\liyang>tnsping ttorcl
TNS Ping Utility for 64-bit Windows: Version 11.2.0.1.0 - Production on 26-3月 -
2014 12:09:48
Copyright (c) 1997, 2010, Oracle. All rights reserved.
已使用的参数文件:
C:\app\liyang\product\11.2.0\client_2\network\admin\sqlnet.ora
已使用 TNSNAMES 适配器来解析别名
尝试连接 (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = 192.1 <===仍然返回成功解析和接受
68.56.11)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = orcl)))
OK (0 毫秒)
------
这个试验二证明了，tnsping 即使在数据库实例停止的情况下，并没有监听1521端口，只要监听运行，tnsping就可以返回正常！
=============
试验三：
那我们再来测试一下，监听停止的情况
------
[oracle@ttdev ~]$ lsnrctl stop
LSNRCTL for Linux: Version 11.2.0.2.0 - Production on 25-MAR-2014 19:26:31
Copyright (c) 1991, 2010, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.56.11)(PORT=1521)))
The command completed successfully
[oracle@ttdev ~]$ lsnrctl status
LSNRCTL for Linux: Version 11.2.0.2.0 - Production on 25-MAR-2014 19:26:39
Copyright (c) 1991, 2010, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.56.11)(PORT=1521)))
TNS-12541: TNS:no listener
TNS-12560: TNS:protocol adapter error
《=======监听停止
TNS-00511: No listener
Linux Error: 111: Connection refused
[oracle@ttdev ~]$ ps -ef | grep smon
oracle 3585 3326 0 19:26 pts/1 00:00:00 grep smon
《===没有数据库实例启动
------
此时，在客户端再次执行 tnsping:
------
C:\Users\liyang>tnsping TTORCL
TNS Ping Utility for 64-bit Windows: Version 11.2.0.1.0 - Production on 26-3月 -
2014 10:27:55
Copyright (c) 1997, 2010, Oracle. All rights reserved.
已使用的参数文件:
C:\app\liyang\product\11.2.0\client_2\network\admin\sqlnet.ora
已使用 TNSNAMES 适配器来解析别名
尝试连接 (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = 192.1
68.56.11)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = orcl)))
TNS-12541: TNS: 无监听程序 <============解析仍然成功，但是报出 TNS-12541 的错误！
------
以上测试说明了，监听停止之后，tnsping 无法被远端监听接受
=============
以下试验四，五开始之前，我们将启动数据库实例和监听
------
[oracle@ttdev admin]$ lsnrctl status
LSNRCTL for Linux: Version 11.2.0.2.0 - Production on 25-MAR-2014 21:02:31
Copyright (c) 1991, 2010, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.56.11)(PORT=1521)))
STATUS of the LISTENER
------------------------
Alias LISTENER
Version TNSLSNR for Linux: Version 11.2.0.2.0 - Production
Start Date 25-MAR-2014 21:01:31
Uptime 0 days 0 hr. 1 min. 0 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /home/oracle/app/oracle/product/11.2.0/dbhome_2/network/admin/listener.ora
Listener Log File /home/oracle/app/oracle/diag/tnslsnr/ttdev/listener/alert/log.xml
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.56.11)(PORT=1521)))
Services Summary...
Service "PLSExtProc" has 1 instance(s).
Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service...
Service "orcl" has 1 instance(s).
Instance "orcl", status READY, has 2 handler(s) for this service...
Service "orclXDB" has 1 instance(s).
Instance "orcl", status READY, has 1 handler(s) for this service...
The command completed successfully
[oracle@ttdev admin]$ ps -ef | grep smon
oracle 4148 1 0 21:01 ? 00:00:00 ora_smon_orcl
oracle 4261 3326 0 21:02 pts/1 00:00:00 grep smon
------
试验四：
删除本地的 tnsnames.ora，之后看一下会出现什么情况
------
C:\Users\liyang>tnsping TTORCL
TNS Ping Utility for 64-bit Windows: Version 11.2.0.1.0 - Production on 26-3月 -
2014 10:31:38
Copyright (c) 1997, 2010, Oracle. All rights reserved.
已使用的参数文件:
C:\app\liyang\product\11.2.0\client_2\network\admin\sqlnet.ora
TNS-03505: 无法解析名称 《=====================这次，连解析都无法成功！
------
注：编辑tnsnames.ora，如果我将TTORCL 修改为 ORCL，则返回同样的结果
------
C:\Users\liyang>tnsping TTORCL
TNS Ping Utility for 64-bit Windows: Version 11.2.0.1.0 - Production on 26-3月 -
2014 10:33:36
Copyright (c) 1997, 2010, Oracle. All rights reserved.
已使用的参数文件:
C:\app\liyang\product\11.2.0\client_2\network\admin\sqlnet.ora
TNS-03505: 无法解析名称
------
=============
试验五：
再来测试一个IP地址输入错误的情景
修改tnsnames.ora文件，从192.168.56.11 改为一个不存在的192.168.56.12
------
TTORCL =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.56.12)(PORT = 1521)) 《==更改IP
)
(CONNECT_DATA =
(SERVICE_NAME = orcl)
)
)
------
C:\Users\liyang>ping 192.168.56.12
正在 Ping 192.168.56.12 具有 32 字节的数据:
来自 192.168.56.1 的回复: 无法访问目标主机。 <====ping 显示了该IP不存在
C:\Users\liyang>tnsping ttorcl
TNS Ping Utility for 64-bit Windows: Version 11.2.0.1.0 - Production on 26-3月 -
2014 11:54:25
Copyright (c) 1997, 2010, Oracle. All rights reserved.
已使用的参数文件:
C:\app\liyang\product\11.2.0\client_2\network\admin\sqlnet.ora
已使用 TNSNAMES 适配器来解析别名
尝试连接 (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = 192.1
68.56.12)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = orcl)))
TNS-12535: TNS: 操作超时 《=======结果是等了较长时间报出超时错误
------
总结：
tnsping 用于诊断各种客户端连接问题还是一个非常好的工具。
但是我们要清楚的知道，这个工具能做什么（检查客户端TNS配置），什么不能做（检查数据库实例是否启动，监听端口是否在1521上）！
从以上试验我们看到，tnsping的解析成功仅仅意味着本地的tnsnames.ora ，IP地址，TNS_ADMIN 变量等配置成功。
但是，完全跟目标数据库实例连接没有任何关系！
最后，sqlnet 跟数据库也完全是独立的两个问题。不要因为sqlnet连接方面出错，就肯定是数据库的问题。要从客户端自身先找原因。
