If your linked server connection doesn't work, you won't get far when you try to run distributed queries. Here are some common problems you might encounter when configuring the Oracle client, along with ways to overcome them:
- Receiving an Invalid Login message. This problem occurs when the login you use to connect to the linked server isn't valid on the Oracle server. To test the login's validity, first try to connect using the Oracle sample Scott/tiger user ID and password.
- Receiving the message Credential Retrieval Failed. This message appears when the client machine is trying to use NTS authentication and authentication is failing. You can correct this problem by commenting out the following parameter in the sqlnet.ora file on the client machine: #Sqlnet.Authentication_services = (NTS). (The # symbol designates a comment). You can find the sqlnet.ora file in the \oracle\ora92\network\ADMIN directory.
- Can't connect from a WAN link or from a different subnet. This problem can occur when the Oracle listen port isn't available. Make sure port 1521 is open. If this port is open, double-check the Oracle listener's configuration to determine whether the default port has changed.