listener.ora文件与tnsnames.ora之间的关系
listener.ora 文件里面的内容如下:
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = d10063)(PORT = 1521))
)
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC0))
)
)
)
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = D:\oracle\ora92)
(PROGRAM = extproc)
(GLOBAL_DBNAME = gsid)
(ORACLE_HOME = D:\oracle\ora92)
(SID_NAME = paul)
(GLOBAL_DBNAME = paul)
(ORACLE_HOME = D:\oracle\ora92)
(SID_NAME = paul)
)
)
tnsnames.ora文件内容如下:
PAUL =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.1.163)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = paul)
)
)
PRIMARY =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.1.163)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = gsid)
)
)

SQL> show parameter service_names
NAME TYPE VALUE
------------------------------------ ----------- -----------
service_names string gsid, paul,paultest
由以上可知道 监听提供静态和动态注册服务名
而tnsnames.ora文件 根据服务名进行客户端连接
而primary这些是连接字符串

C:\Documents and Settings\Paul Yi>lsnrctl status
LSNRCTL for 32-bit Windows: Version 9.2.0.4.0 - Production on 18-DEC-2007 09:47:
21
Copyright (c) 1991, 2002, Oracle Corporation. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=d10063)(PORT=1521)))
STATUS of the LISTENER
------------------------
Alias LISTENER
Version TNSLSNR for 32-bit Windows: Version 9.2.0.4.0 - Produc
tion
Start Date 18-DEC-2007 09:40:34
Uptime 0 days 0 hr. 6 min. 46 sec
Trace Level off
Security OFF
SNMP OFF
Listener Parameter File D:\oracle\ora92\network\admin\listener.ora
Listener Log File D:\oracle\ora92\network\log\listener1.log
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=d10063.avocado.local)(PORT=1521)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(PIPENAME=\\.\pipe\EXTPROC0ipc)))
Services Summary...
Service "gsid" has 2 instance(s).
Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service...
Instance "paul", status READY, has 1 handler(s) for this service...
Service "paul" has 1 instance(s).
Instance "paul", status READY, has 1 handler(s) for this service...
Service "paultest" has 1 instance(s).
Instance "paul", status READY, has 1 handler(s) for this service...
The command completed successfully
从lsnrctl status 处可以看出

初始化参数设置：instance_name=paul service_names=paul,gsid ,paultest

所以动态注册时也会对外提供三个服务：paul和gsid ,paultest

C:\Documents and Settings\Paul Yi>tnsping primary
TNS Ping Utility for 32-bit Windows: Version 9.2.0.4.0 - Production on 18-DEC-20
07 09:50:59
Copyright (c) 1997 Oracle Corporation. All rights reserved.
Used parameter files:
D:\oracle\ora92\network\admin\sqlnet.ora

Used TNSNAMES adapter to resolve the alias
Attempting to contact (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)
(HOST = 192.168.1.163)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = gsid)))
OK (0 msec)
所以综上所述:instance_name只有唯一的一个名称,而service_name可以有多个用于tnsnames.ora客户端连接
连接字符串也可以随意取名
对于客户端来说，它不用关心数据库的名字、实例名到底是什么，它只需要知道数据库对外提供的服务名就行了，这个名字可能和实例名一样，也可能不一样。