This is a 2 node 11gR2 RAC cluster database.
When attempting to configure an ODBC connection to Oracle I encountered an issue with the scan listener and the client firewall. It seems even though I was able to obtain a successful tnsping to the database:
However, trying to connect via ODBC produced the following error:
Instead of pursuing the cumbersome process of dealing with a network team and trying to figure out the firewall issue I simply converted the tnsnames.ora entry to reflect each of the hosts:
I still had a good tnsping, so I moved on to the ODBC DSN again….finally having success:
There are a lot of articles related to this error, but most seem to point to the client side firewall blocking communication. Keep in mind that the client side needs to be able to resolve not just the SCAN , but the VIPs and the real IP’s of all servers in the RAC.