使 Oracle 能同时访问多个SQL Server 的设置方法

如何在Oracle里设置访问多个SQL Server数据库？假设我们要在Oracle里同时能访问SQL Server里默认的pubs和Northwind两个数据库。  

1、在安装了Oracle9i Standard Edition或者Oracle9i Enterprise Edition的windows机器上(Server IP:192.168.0.2), 产品要选了透明网关(Oracle Transparent Gateway)里访问Microsoft SQL Server数据库：ORACLE9I_HOME\tg4msql\admin下新写initpubs.ora和initnorthwind.ora配置文件。  

initpubs.ora内容如下:  
HS_FDS_CONNECT_INFO="SERVER=SQLSERVER_HOSTNMAE;DATABASE=pubs"
HS_DB_NAME=pubs
HS_FDS_TRACE_LEVEL=OFF
HS_FDS_RECOVERY_ACCOUNT=RECOVER
HS_FDS_RECOVERY_PWD=RECOVER

initnorthwind.ora内容如下: 
HS_FDS_CONNECT_INFO="SERVER=sqlserver_hostname;DATABASE=Northwind"
HS_DB_NAME=Northwind
HS_FDS_TRACE_LEVEL=OFF
HS_FDS_RECOVERY_ACCOUNT=RECOVER
HS_FDS_RECOVERY_PWD=RECOVER

$ORACLE9I_HOME\network\admin 下listener.ora内容如下: 
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.0.2)(PORT = 1521))
)
)
)
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(GLOBAL_DBNAME = test9)
(ORACLE_HOME = d:\oracle\ora92)
(SID_NAME = test9)
)
(SID_DESC=
(SID_NAME=pubs)
(ORACLE_HOME=d:\Oracle\Ora92)
(PROGRAM=tg4msql)
)
(SID_DESC=
(SID_NAME=northwind)
(ORACLE_HOME=d:\Oracle\Ora92)
(PROGRAM=tg4msql)
)
) 　

重启动这台做gateway的Windows机器上(IP:192.168.0.2)TNSListener服务(凡是按此步骤新增可访问的SQL Server数据库时，TNSListener服务都要重启动)。  

2、Oracle8i、Oracle9i的服务器端配置tnsnames.ora, 添加下面的内容: 
pubs =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.0.2)(PORT = 1521))
)
(CONNECT_DATA =
(SID = pubs)
)
(HS = pubs)
)
northwind =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.0.2)(PORT = 1521))
)
(CONNECT_DATA =
(SID = northwind)
)
(HS = northwind) )

保存tnsnames.ora后,在命令行下： 
tnsping pubs
tnsping northwind 
出现类似提示，即为成功:  

Attempting to contact (DESCRIPTION = (ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.0.2)
(PORT = 1521))) (CONNECT_DATA = (SID = pubs)) (HS = pubs))
OK（20毫秒）
Attempting to contact (DESCRIPTION = (ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.0.2)
(PORT = 1521)))
(CONNECT_DATA = (SID = northwind)) (HS = northwind))OK（20毫秒）

设置数据库参数global_names=false，不要求建立的数据库链接和目的数据库的全局名称一致。global_names=true则要求, 多少有些不方便。  

oracle9i和oracle8i都可以在DBA用户下用SQL命令改变global_names参数alter system set global_names=false，建立公有的数据库链接:  

create public database link pubs
connect to testuser identified by testuser_pwd using 'pubs';
create public database link northwind
connect to testuser identified by testuser_pwd using 'northwind';

(假设SQL Server下pubs和northwind已有足够权限的用户登陆testuser,密码为testuser_pwd)

访问SQL Server下数据库里的数据:  

select * from stores@pubs;
...... ......select *
from region@northwind;
...... ...... 

3、使用时的注意事项： 
ORACLE通过访问SQL Server的数据库链接时，用select * 的时候字段名是用双引号引起来的。 
例如： 
create table stores as select * from stores@pubs;
select zip from stores；
ERROR 位于第 1 行:
ORA-00904: 无效列名
select "zip" from stores;
zip
-----
98056
92789
96745
98014
90019
89076

已选择6行,用SQL Navigator或Toad看从SQL Server转移到ORACLE里的表的建表语句为:
CREATE TABLE stores
("stor_id" CHAR(4) NOT NULL,
"stor_name" VARCHAR2(40),
"stor_address" VARCHAR2(40),
"city" VARCHAR2(20),
"state" CHAR(2),
"zip" CHAR(5))
PCTFREE 10
PCTUSED 40
INITRANS 1
MAXTRANS 255
TABLESPACE users
STORAGE (
INITIAL 131072
NEXT 131072
PCTINCREASE 0
MINEXTENTS 1
MAXEXTENTS 2147483645
)  

总结: 
Windows下Oracle9i网关服务器在$Oracle9i_HOME\tg4msql\admin目录下的initsqlserver_databaseid.ora。
Windows下Oracle9i网关服务器listener.ora里面： 
(SID_DESC=
(SID_NAME=sqlserver_databaseid)
(ORACLE_HOME=d:\Oracle\Ora92)
(PROGRAM=tg4msql)
)

UNIX或WINDOWS下ORACLE8I,ORACLE9I服务器tnsnames.ora里面：
northwind =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.0.2)(PORT = 1521))
)
(CONNECT_DATA =
(SID = sqlserver_databaseid)
)
(HS = sqlserver_databaseid)
)
需要sqlserver_databaseid一致才行。