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 是一個oracle數據庫網絡配置文件，通過這個配置文件才能建立對數據庫的連接。這個文件通常位於"ORACLEHOME(oracle數據庫的安裝目錄)\NETWORK\ADMIN\ 目錄下
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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>是自定義的名字。就是把下面的連接特定IP+端口+數據庫實例的這個連接命名一下，連接時就直接用該名字來指定連接。
<hostname>可以是主機名，可以是IP.填寫數據庫服務器所在機器IP。如在本機則爲127.0.0.1或localhost
<port>默認爲1521.這個端口是oracle數據庫服務端口號
<service_name>是數據庫實例名，你要連接的數據庫實例。
Here is a completed example:下面是一個完整的例子
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同時存在於數據庫客戶端與服務器端（客戶端與服務端不在同一臺主機中）。如果在客戶端連遠程的數據庫服務器，你就要編輯客戶機上的tnsnames.ora。數據庫服務端主機上的tnsnames.ora則可以不編輯。如果你在數據庫服務端所在機器上登錄連接數據庫，你就要編輯服務端的tnsnames.ora。客戶端的可以不編輯。