这个目录下可以看到以下initdg4msql.ora文件，上面在安装透明网关的时候有配置的要链接SQL SERVER数据的地址和数据库名称，在这里都可以体现：

 # This is a customized agent init file that contains the HS parameters

 # that are needed for the Database Gateway for Microsoft SQL Server

 #

 # HS init parameters

 #

 HS_FDS_CONNECT_INFO=[127.0.0.1]://DEMO   注：连接其他的SQL Server可修改此处

 HS_FDS_TRACE_LEVEL=OFF

 HS_FDS_RECOVERY_ACCOUNT=RECOVER

 HS_FDS_RECOVERY_PWD=RECOVER

 # This is a sample listener.ora that contains the NET8 parameters that are

 # needed to connect to an HS Agent

 LISTENER =

  (ADDRESS_LIST=

       (ADDRESS=(PROTOCOL=tcp)(HOST=localhost)(PORT=))

  )

 SID_LIST_LISTENER=

   (SID_LIST=

       (SID_DESC=

          (SID_NAME=dg4msql)

          (ORACLE_HOME=D:\Oracle\product\11.2.\dbhome_1)

          (PROGRAM=dg4msql)

       )

   )

 #CONNECT_TIMEOUT_LISTENER =  

 # This is a sample tnsnames.ora that contains the NET8 parameters that are

 # needed to connect to an HS Agent

 dg4msql  =

   (DESCRIPTION=

     (ADDRESS=(PROTOCOL=tcp)(HOST=localhost)(PORT=))

     (CONNECT_DATA=(SID=dg4msql))

     (HS=OK)

   ) 

 # This is a sample listener.ora that contains the NET8 parameters that are

 # needed to connect to an HS Agent

 SID_LIST_LISTENER =

   (SID_LIST =

     (SID_DESC =

       (SID_NAME = CLRExtProc)

       (ORACLE_HOME = D:\Oracle\product\11.2.\dbhome_1)

       (PROGRAM = extproc)

       (ENVS = "EXTPROC_DLLS=ONLY:D:\Oracle\product\11.2.0\dbhome_1\bin\oraclr11.dll")

     )

     (SID_DESC=

          (SID_NAME=dg4msql)

          (ORACLE_HOME=D:\Oracle\product\11.2.\dbhome_1)

          (PROGRAM=dg4msql)

     )

   )

 LISTENER =

   (DESCRIPTION_LIST =

     (DESCRIPTION =

       (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))

       (ADDRESS = (PROTOCOL = TCP)(HOST = YRDLG5GS4G3ODYI)(PORT = ))

       (ADDRESS=(PROTOCOL=tcp)(HOST=127.0.0.1)(PORT=))

     )

   )

 ADR_BASE_LISTENER = D:\Oracle

 #CONNECT_TIMEOUT_LISTENER =  

 这里需要注意的主要是一下几点：

 PROGRAM为dg4msql：因为实例的配置文件在dg4msql目录下，就是上面的initdg4msql.ora文件所在的目录

 SID_NAME为dg4msql：这个sid就是上面的文件名中的sid，initdg4msql.ora的sid为dg4msql

 ORACLE_HOME就是我们透明网关的安装目录

 ORACLE的监听端口是1521，我的oracle和透明网关是安装在同一台机器上的，所以透明网关的监听端口设置为1522。

 一个initSID.ora文件就对应一个SID_DESC，可以根据想要链接的数据库来配置。

 # sqlnet.ora Network Configuration File: D:\Oracle\product\11.2.\dbhome_1\network\admin\sqlnet.ora

 # Generated by Oracle configuration tools.

 # This file is actually generated by netca. But if customers choose to

 # install "Software Only", this file wont exist and without the native

 # authentication, they will not be able to connect to the database on NT.

 SQLNET.AUTHENTICATION_SERVICES= (NONE)

 NAMES.DIRECTORY_PATH= (TNSNAMES, EZCONNECT)

 # This is a sample tnsnames.ora that contains the NET8 parameters that are

 # needed to connect to an HS Agent

 ORCL =

   (DESCRIPTION =

     (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = ))

     (CONNECT_DATA =

       (SERVER = DEDICATED)

       (SERVICE_NAME = orcl)

     )

   )

 dg4msql  =

   (DESCRIPTION=

     (ADDRESS=(PROTOCOL=tcp)(HOST=127.0.0.1)(PORT=))

     (CONNECT_DATA=(SID=dg4msql))

     (HS=OK)

   ) 

 命令：lsnrctl reload

 SELECT * FROM user_sys_privs where privilege like upper('%DATABASE LINK%')

 如：grant create public database link to system ;

 格式：grant create public database link to 用户名 ;

 查询dblink：

 select * from dba_db_links;

 删除dblink：

 DROP DATABASE LINK [name];  

 create database link DBTEST1

   connect to SA identified by "password"

   using 'dg4msql';

 格式：

 create database link DBLink名称
   connect to SQL Server账户 identified by "SQL Server密码"

   using 'SID';