Toad 10.6 and 10.5 Connection dialogue is not working with comma separated TNS aliases entries. In Toad 10.1 it was still working fine.
I have an environment that make extensive use of comma separated entries in their tnsnames.ora. In 10.6 the New Connection dialogue box adds a comma to the end of the resolved entries on the Database drop down list. This will result in the error " Ora-12154" when trying to connect.
Here's a an example of my tnsnames.ora:
Manually remove the comma from the DB drop down list or from the TNS name Editor window.
Issue fixed in version 11.0. The latest version can be downloaded from: