You need to make sure the web applications and customizations are in place before you mount the content database to the web application. The full process is described in the article Upgrade content databases to SharePoint 2013:
Create Web Applciations
Create a web application for each web application that existed in the SharePoint 2010 Products environment. For each web application, do the following:
Use the same URL (including name, port, and host header) and configure alternate-access mapping settings.
If you use a different URL, Office applications might not be redirected correctly to the new URLs and all bookmarks to the old URLs will not work.
Use the same authentication method.
For example, if you use Windows Classic authentication in your old environment, and you want to continue to use it, then you must create a web application that uses Windows Classic authentication. Because claims-based authentication is now the default option for SharePoint 2013, you must use Windows PowerShell to create a web application that uses Windows Classic authentication. For more information, see Create web applications that use classic mode authentication in SharePoint 2013 and Create claims-based web applications in SharePoint 2013.
Alternatively, you can migrate to claims authentication. For more information, see Migrate from classic-mode to claims-based authentication in SharePoint 2013.
Recreate included paths.
Recreate quota templates.
Configure email settings for the web application.
For more information, see Configure email integration for a SharePoint 2013 farm.
Enable self-service site creation for any web application that used it in the previous environment. Recreate any self-service site creation settings.
Create the managed path for the My Sites (/personal) on the web application that hosts My Sites. My Sites are available in SharePoint Server only.
Recreate any web application policies or other web application settings that you had configured in the previous environment.
One frequent cause of failures during upgrade is that the new environment does not have customized features, solutions, or other elements. Make sure that all custom elements from the SharePoint 2010 Products environment are installed on your front-end web servers before you upgrade any content databases.
In this step, you manually transfer all customizations to your new farm. Make sure to install any components that your sites depend on to work correctly, such as the following:
- Custom site definitions
- Custom style sheets, such as cascading style sheets, and images
- Custom Web Parts
- Custom Web services
- Custom features and solutions
- Custom assemblies
- Web.config changes (such as security)
Ensure that you transfer all unique settings from the Web.config files for each web application to the new servers.
- Administrator-approved form templates (.xsn files) and data connection files (.udcx files) for InfoPath. InfoPath is available in SharePoint Server 2010 only.
Any other components or files on which your sites depend.
SharePoint 2013 can host sites in both SharePoint 2010 Products and SharePoint 2013 modes. The installation for SharePoint 2013 contains both SharePoint 2010 Products and SharePoint 2013 versions of many elements. The directories on the file system are duplicated in both the 14 and 15 paths, for example:
- Web Server Extensions/14/TEMPLATE/Features
- Web Server Extensions/15/TEMPLATE/Features
There are also two versions of the IIS support directories: _Layouts, _Layouts/15 and _ControlTemplates, _ControlTemplates/15.
Be sure to install customizations to the correct location in your new farm. For example, additional style sheets for SharePoint 2010 Products should be installed in the /14 path, not the new /15 path so that site collections that you haven’t upgraded can use them. If you want a solution to be available to both paths, install it two times, and the second time use the CompatibilityLevel parameter when you install it, and it will be installed to the /15 path. For more information, see Install-SPSolution.
For more information about how to update customizations for use in SharePoint 2013, see Redeploying Customizations and Solutions in SharePoint Foundation 2010 and SharePoint Server 2010. For more information about how to deploy customizations to your environment, see Install and manage solutions for SharePoint 2013.
When all this is done, you need to verify custom components by
Stsadm -o enumallwebs -includefeatures -includewebparts
This operation can report the templates, features, Web Parts, and other custom elements that are used for each site.
Run Test-SPContentDatabase to see if you're missing any solutions, features, managed paths or templates in your 2013 Web App.
Test-SPContentDatabase -name WSS_Content_DB -webapplication http://sitename
Follow the messeges and add the missing configuration/solutions/templates to your web app.