I have a some instances running on Sitecore 8.1 .I want to upgrade these instances to Sitecore 9.1.
I know that I should use MS-SQL-2016 to support XDB. I want to install Sitecore-9.1 directly and use the old SQL data.
My question is : For Sitecore 8.1's SQL data . Do I need use some tool or scripts to migrating these data . Or just do a backup and restore into MS-SQL-2016?