WORKAROUND:
Toad for Oracle only works with Oracle databases.
If you want to connect to a DB2 database, Toad Data Point / Toad Intelligence Central or Toad for DB2 are the appropriate programs.
Toad Data Point allows you to connect, query and prepare data. Viceversa, Toad for DB2 simplify database management.
For more information about both products check on Toad Data Point site and Toad for DB2 site.