How do you setup a linked server to an Oracle database on SQL 2000/2005?

Question

I am able to create and execute a DTS package that copies tables from a remote Oracle database to a local SQL server, but want to setup the connection to the Oracle database as a linked server.

The DTS package currently uses the Microsoft OLE DB Provider for Oracle with the following properties:

• Data Source: SERVER=(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=10.1.3.42)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=acc)));uid=UserName;pwd=UserPassword;
• Password: UserPassword
• User ID: UserName
• Allow saving password: true

How do I go about setting a linked server to an Oracle database using the data source defined above?

Answer 1

I was able to setup a linked server to a remote Oracle database, which ended up being a multi-step process:

1. Install Oracle ODBC drivers on SQL Server.
2. Create System DSN to Oracle database on SQL Server.
3. Create linked server on SQL server using System DSN.

Step 1: Install Oracle ODBC drivers on server

a. Download the necessary Oracle Instant Client packages: Basic, ODBC, and SQL*Plus (optional)

b. Unzip the packages to a local directory on the SQL server, typically C:\Oracle. This should result in a [directory] like *C:\Oracle\instantclient_10_2*, which will be the value of [directory] referenced in the rest of this answer.

c. Create a text file named tnsnames.ora within the instant client [directory] that contains the following:

OracleTnsName = 
(
  DESCRIPTION=
  (
    ADDRESS = (PROTOCOL=TCP)(HOST=10.1.3.42)(PORT=1521)
  )
  (
    CONNECT_DATA = (SERVICE_NAME=acc)
  )
)

Note: Actual HOST, PORT, and SERVICE_NAME will vary based on Oracle server you are establishing a connection to. This information can often be found using the Oracle network client tools under the listeners.

The OracleTnsName can be any name you want to assign to the Oracle data source, and will be used when setting up the system DSN. You can also use the syntax above to define multiple TNS names in the same tnsnames.ora file if desired.

d. Add the [directory] to the system PATH environment variable.

e. Create a new system environment variable named TNS_Admin that has a value of [directory]

f. Execute the [directory]**odbc_install.exe** utility to install the Oracle ODBC drivers.

g. It is recommended that you reboot the SQL server, but may not be necessary. Also, you may want to grant security permissions to this directory for the SQL server and SQL agent user identities.

Step 2: Create a System DNS that uses the Oracle ODBC driver

a. Open the ODBC Data Source Administrator tool. [ Administrative Tools --> Data Sources (ODBC) ]

b. Select the System DSN tab and then select the Add button.

c. In the drivers list, select Oracle in instantclient {version}. (e.g. 'Oracle in instantclient 10_2') and then select Finish button.

d. Specify the following:

• Data Source Name: {System DSN Name}
• Description: {leave blank/empty}
• TNS Service Name: should have the OracleTnsName you defined in the tnsnames.ora file listed, select it as the value.
• User ID: {Oracle user name}

e. Select Test Connection button. You should be prompted to provide the {Oracle user password}. If all goes well the test will succeed.

Step 3: Create linked server in SQL to the Oracle database

Open a query window in SQL server and execute the following:

EXEC sp_addlinkedserver 
     @server  = '{Linked Server Name}'
    ,@srvproduct = '{System DSN Name}'
    ,@provider  = 'MSDASQL'
    ,@datasrc  = '{System DSN Name}'

EXEC sp_addlinkedsrvlogin 
     @rmtsrvname = '{Linked Server Name}'
    ,@useself  = 'False'
    ,@locallogin = NULL
    ,@rmtuser  = '{Oracle User Name}'
    ,@rmtpassword = '{Oracle User Password}'

Note: The {Linked Server Name} can be anything you want to use when referencing the Oracle server, but the {System DNS Name} must match the name of the system DSN you created previously.

The {Oracle User Name} should be the same as the User ID used by the system DSN, and the {Oracle User Password} should be the same as you used to sucessfully test the ODBC connection. See KB 280106 for information on troubleshooting Oracle linked server issues.

Querying the Oracle linked server

You may use OPENQUERY to execute pass-through queries on the Oracle linked server, but be aware that for very large recordsets you may recieve a ORA-01652 error message if you specify a ORDER BY clause in the pass-through query. Moving the ORDER BY clause from the pass-through query to the outer select statement solved this issue for me.

Answer 2

Hi... This was very useful, I was able to create the linked server from SQL2000 to Oracle 9i, run queries, etc (had to set up a function in Oracle that will set up certain session parameters first, but it works)... One question, in case you know... I need to create a persistent connection or session... Explaining myself: The Oracle DBA tells me that it would be great if the connection from SQL to Oracle is active all day long... This will save some Oracle related problems (which I don't understand very well), but the most important thing in my side is that I won't need to set the session parameters every time I need to run a query... According to some tests we ran, every time I run a query, or set a parameter, the session stays alive for aprox. 30 seconds, then it drops, meaning that the next time I run a query, I need to first set the session parameters again, o else the query won't bring any data

Any ideas on how I can do this?? I've been googling a lot, but with no luck

Thanks!!

Answer 3

I had the same problem. I was on the phone with Microsoft for hours, and they did not have a solution. None of those "connection timeout" settings helped me.

To resolve it, I created a DTS job that runs a proc which only updates the time on one row, in one column, every two minutes. Then I setup a replication between SQL Server and Oracle, scheduled to replicate that single cell change, from SQL to Oracle, every 3 minutes. It keeps the connection alive!