I am getting tns-03505 error when attempting to connect to the database. Nothing changed since yesterday and yesterday it was working. I am able ping the ip address but when I do tnsping it says 'failed to resolve name'.
What can possibly be wrong?
I've looked at tnsnames.ora, everything there the same as yesterday.
I would suggest that you recheck your tnsnames.ora file again and make suer that the listeners are up and running.
03505, 00000, "Failed to resolve name"
// *Cause: The service name you provided could not be found in TNSNAMES.ORA, an Oracle Names server, or a native naming service.
// *Action: Verify that you entered the service name correctly. You may need to ensure that the name was entered correctly into the network configuration.
Also check your sqlnet.ora and make suer that the resolution methods are mentioned and if there any domain name extension, then you have to use it on your service name under tnsnames.ora file.
What OS ? If its NT, try creating another test service name to the database you wanted and see the test is successful and you could connect to it. If you could then there is something goofy, try replacing the host name with the ipaddress of hostname and try.
I Don't think, tnsnames path which was working yesterday is something to do with registry. DOn't play with registry unless otherwise you have to.
As sambavan suggested, try stopping your networking components(Listener, dbsnmp agent, data gatherer) and restart 'em and try connecting to database.