The 20.00 release can co-exist with the 15.10.10.00 release and later versions. The active release is the most recent release installed. For example, if 15.10.10.00 is installed, then 15.10.10.00 is the active release. If 20.00 is installed after installing 15.10.10.00, 20.00 becomes the active release. The releases can be installed in any order. Installing 20.00 then 15.10.10.00 makes 15.10.10.00 the active release.
An application named ListProducts is located in the Teradata Client 20.00 folder under Applications. ListProducts can be used to list the products installed and change the active release. The difference between the active release and non-active release is that the bin folder will be on PATH. For details on how to change the default behavior, see Install Configuration File.
The notion of an active release does not apply when TTU software is installed on a shared location.