tnsnames.ora 是什么

Tnsnames.ora

TNSNAMES.ORA is a SQL*Net configuration file that defines databases addresses for establishing connections to them. This file normally resides in the ORACLE HOME\NETWORK\ADMIN directory.

tnsnames.ora 是一个oracle数据库网络配置文件，通过这个配置文件才能建立对数据库的连接。这个文件通常位于"ORACLEHOME(oracle数据库的安装目录)\NETWORK\ADMIN\ 目录下

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[edit]Configuring TNSNAMES.ora

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Add the following entry in your TNSNAMES.ORA file and change the values shown in brackets to suit your environment:

<addressname> = (DESCRIPTION =   (ADDRESS_LIST =     (ADDRESS = (PROTOCOL = TCP)(Host = <hostname>)(Port = <port>))   ) (CONNECT_DATA =   (SERVICE_NAME = <sid>) ))

<addrssname>是自定义的名字。就是把下面的连接特定IP+端口+数据库实例的这个连接命名一下，连接时就直接用该名字来指定连接。

<hostname>可以是主机名，可以是IP.填写数据库服务器所在机器IP。如在本机则为127.0.0.1或localhost

<port>默认为1521.这个端口是oracle数据库服务端口号

<service_name>是数据库实例名，你要连接的数据库实例。

Here is a completed example:下面是一个完整的例子

ORA11 =  (DESCRIPTION =    (ADDRESS_LIST =     (ADDRESS = (PROTOCOL = TCP)(HOST = 127.0.0.1)(PORT = 1521))    ) (CONNECT_DATA =   (SERVICE_NAME = ORA11) ))

The TNSNAMES.ORA files are located on both client and server systems. If you make configuration changes on the server ($ORACLE_HOME/network/admin/tnsnames.ora) ensure you can connect to the database through the listener if you are logged on to the server. If you make configuration changes on the client (c:\oracle\product\10.2.0\db_1\network\admin\tnsnames.ora) ensure you can connect from your client workstation to the database through the listener running on the server.

tnsnames.ora同时存在于数据库客户端与服务器端（客户端与服务端不在同一台主机中）。如果在客户端连远程的数据库服务器，你就要编辑客户机上的tnsnames.ora。数据库服务端主机上的tnsnames.ora则可以不编辑。如果你在数据库服务端所在机器上登录连接数据库，你就要编辑服务端的tnsnames.ora。客户端的可以不编辑。