On an upgraded instance to Sitecore 9, we are getting the following exception:
Could not resolve type name: Sitecore.Data.SqlServer.SqlServerProxyDataProvider, Sitecore.Kernel (method: Sitecore.Configuration.DefaultFactory.CreateFromTypeName(XmlNode configNode, String[] parameters, Boolean assert)).
If you decompile Sitecore.Kernel.Dll on your old Sitecore Version and compare it with one on Sitecore 9, you will notice that Sitecore.Data.Proxies namespace has been deprecated now. Additionally ProxyDisabler is no more exists with Sitecore 9.
Conclusion: There are no feasible alternate on Sitecore 9 for Proxies.
For more details please refer to this Sitecore Stack Exchange question and a blog post from Brian Pederson.
Hope this helps.
Sitecore Competencies 
I ran into this issue
Heartbeat 13:23:48 ERROR Could not resolve type name: Sitecore.Data.SqlServer.SqlServerProxyDataProvider, Sitecore.Kernel (method: Sitecore.Configuration.DefaultFactory.CreateFromTypeName(XmlNode configNode, String[] parameters, Boolean assert)).
Heartbeat 13:23:48 ERROR Exception in heartbeat event subscriber (index: 7).
how did you fixed it ?
LikeLike