Security for Oracle linked server from SQL Server I'm trying to make the linked server from SQL Server 2005 to Oracle more secure by not having user/pass on "Be made using this security context:" fields so only a specific user can access the data from linked server.

So I tried mapping SQL Security User to Oracle user/pass by inserting it in "Local server login to remote server login mappings:" area then "For a login not defined in the list above, connection will:" set to "Not be made".

When I click OK, I get:

Access to the remote server is denied because no login-mapping exists


Is it not possible to map SQL login to a Oracle login? Is there any way to get this to work?
If the user that you added to use the Linked Server is not for the login you are currently using (and it is the only one you've set up), when you click OK, the connection test will fail because the current user will have no valid mapping to use the Linked Server.

To fix this simply create a valid mapping for your login as well. That way when you click OK the test will succeed because there is a valid mapping for the current user - if you use the same settings for the Oracle target in both mappings you'll have some confidence that it will be working for the other user(s).   Either that or ignore the error from the test and check specifically that the user you created the mapping for can use the linked server successfully.