Presently only MSSQL Servers 2008, 2012, 2014, and 2016 is offically supported up to DocuWare version 7. This is because MSSQL Server 2017 was released in October 2017 which was too late to include in DocuWare 7. (DocuWare 6.12 was released prior to MSSQL 2017 release).
I expect MSSQL 2017 to be officially supported with the release of DocuWare 7.1.
Senior Director Support Americas