If installed on the same machine, Tectia Client and Tectia Server should always be upgraded to be the same version, because there are dependencies between the common components.
Check if you have some Secure Shell software, such as earlier versions of Tectia products or third-party Secure Shell server or client, running on the machine where you are planning to install the new Tectia versions.
In the following cases you must uninstall the existing version of Tectia Client/Server before installing version 6.6.3:
Your existing version is 4.x.
You are installing on Solaris.
In any other case you can upgrade to Tectia Client/Server 6.6.3 without first uninstalling the existing version. The existing version will be automatically removed from the host during the installation procedure.