Related: Connecting SQL Server and Oracle Using Linked Servers

SQL Server Linked Servers feature lets you access Oracle data and data from other OLE DB/ODBc compatible data sources from SQL Server. Here are the basic steps for setting up an Oracle linked server.

1. Install and Configure the Oracle Client Software

Oracle client software provides the network libraries required to establish connectivity to an Oracle database system.Download the software from http://www.oracle.com/technology/software/products/database/oracle10g/index.html. Install the software on your SQL Server system and configure it by using Oracle Net Configuration Assistant.

2. Create the Linked Server

Create a linked server by using the T-SQL command

EXEC sp_addlinkedserver
  'OracleLinkedServer', 'Oracle',
  'MSDAORA', 'OracleServer'

The name of the linked server is Oracle-LinkedServer.The second parameter, product name (Oracle),is optional.The third parameter specifies the OLE DB provider. MSDAORA is the name of the Microsoft OLE DB Provider for Oracle.The final required parameter is the data source name, Oracle Server.

3. Add Logins for the Linked Server

Next, provide the SQL Server system with an Oracle login to access the Oracle database by using the sp_addlinkedsrvlogin command

EXEC sp_addlinkedsrvlogin '
  OracleLinkedServer ', false,
  'SQLuser', 'OracleUser',
  'OraclePwd'

The first parameter, Oracle Linked Server, specifies the name of the linked server system that you created.The second parameter determines the name of the login to be used on the remote system. A value of True indicates that the current SQL Server login will be used to connect to the linked server. This requires that the logins on the two database servers match, which is typically not the case. A value of False means you'll supply the remote login.

The third parameter specifies the name of a SQL Server login that this remote login will map to. A value of NULL indicates that this remote login will be used for all connections to the linked Oracle server. If the Oracle system uses Windows authentication, you can use the keyword domain\ to specify a Windows login. The fourth and fifth parameters supply login and password values for the Oracle system.

4. Query the Linked Server

To test the connection, run a sample query using the linked server name. Linked servers support updates as well as queries.To access the tables on a linked server, use a four-part naming syntax: linked_server_name.catalog_ name.schema_name.table_name. For example, to query the sample Oracle Scott database, you'd enter the statement

SELECT * FROM
  OracleLinkedServer..SCOTT.EMP


5. List the Linked Servers

To list your linked servers and show the OLE DB provider that they employ, use the sp_linkedserver stored procedure.

Related: Troubleshooting Oracle Client Connections