Follow this procedure for connecting to a DB2 database when you do not have an ODBC Datasource defined for it.
To connect to a DB2 database you need to specify:
The connection to the database may be defined to your DB2 Client as an Alias. If so, you can just specify the alias name. AQT cannot give you a dropdown list of these.
There info on how to define an Alias to your DB2 Client at Configuring the DB2 Client.