使 Oracle 能同時訪問多個SQL Server 的設定方法

如何在Oracle裡設定訪問多個SQL Server資料庫？假設我們要在Oracle裡同時能訪問SQL Server裡預設的pubs和Northwind兩個資料庫。  

1、在安裝了Oracle9i Standard Edition或者Oracle9i Enterprise Edition的windows機器上(Server IP:192.168.0.2), 產品要選了透明網關(Oracle Transparent Gateway)裡訪問Microsoft SQL Server資料庫：ORACLE9I_HOME\tg4msql\admin下新寫initpubs.ora和initnorthwind.ora設定檔。  

initpubs.ora內容如下:  
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內容如下: 
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內容如下: 
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)
)
) 　

重啟動這台做gateway的Windows機器上(IP:192.168.0.2)TNSListener服務(凡是按此步驟新增可訪問的SQL Server資料庫時，TNSListener服務都要重啟動)。  

2、Oracle8i、Oracle9i的伺服器端配置tnsnames.ora, 添加下面的內容: 
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) )

儲存tnsnames.ora後,在命令列下： 
tnsping pubs
tnsping northwind 
出現類似提示，即為成功:  

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）

設定資料庫參數global_names=false，不要求建立的資料庫連結和目的資料庫的全域名稱一致。global_names=true則要求, 多少有些不方便。  

oracle9i和oracle8i都可以在DBA使用者下用SQL命令改變global_names參數alter system set global_names=false，建立公有的資料庫連結:  

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';

(假設SQL Server下pubs和northwind已有足夠許可權的使用者登陸testuser,密碼為testuser_pwd)

訪問SQL Server下資料庫裡的資料:  

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

3、使用時的注意事項： 
ORACLE通過訪問SQL Server的資料庫連結時，用select * 的時候欄位名是用雙引號引起來的。 
例如： 
create table stores as select * from stores@pubs;
select zip from stores；
ERROR 位於第 1 行:
ORA-00904: 無效列名
select "zip" from stores;
zip
-----
98056
92789
96745
98014
90019
89076

已選擇6行,用SQL Navigator或Toad看從SQL Server轉移到ORACLE裡的表的建表語句為:
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
)  

總結: 
Windows下Oracle9i閘道伺服器在$Oracle9i_HOME\tg4msql\admin目錄下的initsqlserver_databaseid.ora。
Windows下Oracle9i閘道伺服器listener.ora裡面： 
(SID_DESC=
(SID_NAME=sqlserver_databaseid)
(ORACLE_HOME=d:\Oracle\Ora92)
(PROGRAM=tg4msql)
)

UNIX或WINDOWS下ORACLE8I,ORACLE9I伺服器tnsnames.ora裡面：
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。