We currently have IBM Rational DOORS 9.6.1.6 installed on Windows 2012 R2 Server and our users accessing the DOORS DB via x5 floating licenses. We are considering to swap it with DOORS Web Access if it can easily be migrated as well. I am looking for installation and migration documents. Appreciate any recommendation or hints about the overall process. Thx.

IBM® Engineering Requirements Management DOORS® - Web Access (DWA) gives you web-based access to the requirements in a IBM Engineering Requirements Management DOORS (DOORS) database. So there is no migration. DWA has a separate installation that you configure to communicate with your existing DOORS database. Here are the installation docs: Installing DWA (ibm.com)

Or perhaps you were referring to IBM Engineering Requirements Management DOORS Next? Migrating data to DOORS Next (ibm.com)