使Oracle能同时访问多个SQL Server

   来源：qqread    作者：qqread

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(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=pubsHS_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。

设置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.