What version of Oracle server does Toad 9.018 support?
Please check the "Release Information" for minimum software requirements on the Toad for Oracle page on the Quest website to determine what versions of Oracle the current version of Toad for Oracle supports: http://www.quest.com/toad_for_oracle/release_information.aspx
Toad for Oracle 9.0.1 Minimum Software Requirements
There are also additional requirements for different modules. Please check release information online for most updated information for newest version of Toad.