I needed to migrate a SharePoint 2010 site to SharePoint 2013. So I took the backup of the content database and restored it on SharePoint 2013 SQL Server. Before mounting the database to a site collection in SharePoint 2013 I deployed all the WSP files from SharePoint 2010 to SharePoint 2013.
Then I ran Test-SPContentDatabase command and had the following result:
After some research I found a post by Jerry Yasir. He had an exactly similar issue during up-gradation from 2007 to 2010. The resolution is to restart the SharePoint machine and run the PowerShell command Test-SPContentDatabase again and everything will be fine. I also tried to do iisreset before restarting but that did not help.
References:
http://jerryyasir.wordpress.com/2010/09/05/sharepoint-2010-upgrade-issue-found-45-webs-using-missing-web-template-75820-lcid-1033-in-contentdatabase/
Then I ran Test-SPContentDatabase command and had the following result:
The message was: 4 Sites in database [WSS_Content_DBName] has reference(s) to a missing site definition, Id = [100001], Lcid = [1033], compatibility level =[14]. The site definition with Id 100001 is referenced in the database [WSS_Content_DBName], but is not installed on the current farm for sites with compatibility level 14. The missing site definition may cause upgrade to fail. Please install any solution which contains the site definition and restart upgrade if necessary.
However, the Site definition was deployed properly in the 14 hive as can be seen from the below screenshots:
References:
http://jerryyasir.wordpress.com/2010/09/05/sharepoint-2010-upgrade-issue-found-45-webs-using-missing-web-template-75820-lcid-1033-in-contentdatabase/