While working on SharePoint Migration from 2010 to 2016, I thought it to be smooth because the environment didn’t have any customizations and neither I had any custom solution deployed on it.
So, I started the migration from SharePoint using Content DB. I have migrated Content DB from SharePoint 2010 to 2013. After creating a web application and running “test-spcontentdatabase” PowerShell command (No errors in output), I mounted the content database successfully without any issue.
SharePoint site was working as expected. I have also done the visual upgrade of SharePoint sites without any error. Now, it's time to move to SharePoint 2016. Again, I have to follow the same approach I did in SharePoint 2013.
Moved and restored the Content Database on SQL Server from SharePoint 2013 and created the web applications but when I ran the “Test-Spcontentdatabase” Powershell command, I got an error that I never faced after doing around 10 migrations.
“Legacy Site Detected”
So, I have 2 sites which are still using SharePoint 2010 experience.