title: Purpose of ProjectsV13 LocalDB instance
body: <p>According to <a href="https://stackoverflow.com/a/27201328/145173">this answer</a>, SQL Server Data Tools uses a private LocalDB instance ProjectsV13, which you're not supposed to use for your own applications. Instead, you should use MSSQLLocalDB or your own private instance.</p>
  
  <p>Is this documented anywhere? What does SSDT use its private instance for? (I don't see anything in mine.)</p>
  
  <p>Is a private LocalDB instance basically spinning up a second copy of SQL Server? On the surface, it sounds rather resource intensive to have a dedicated database engine just for tooling metadata. How resource intensive is this really? Does it have a perf impact on starting up and using Visual Studio? If so, and if it's not really needed, can and should you turn it off or consolidate instances in some other way? My guess is not; otherwise, SSDT wouldn't use a private instance, but it would be nice to know how this works under the hood.</p>