Following the migration of our oracle 9i database on windows server 2003 to version 10g with windows 2008 server, I could encounter a problem with the DBLink linking between two databases located in two servers, my Server1 (oracle 10g) in city A and the other Server2 (oracle 9i) in City B, the connection between the server via a VPN. creating DBLink all goes well, but when I want to test the DBLink with TOAD, TOAD is paidre and does not respond, knowing that before migrating all was well.
There is not enough information in your post to be able to diagnose the issue. Does the database link, its username or password contain any non-ASCII characters?
If everything is pure ASCII, you need to open an SR with Oracle Support. They can analyze network traces and diagnose the issue.
SR=Service Request -- reporting a problem on My Oracle Support (support.oracle.com), if you have a valid support contract for the database.
Generally, this is the type of issue that needs diagnosis and the forum is not the best place to get help for it.