Assume that you use Microsoft SQL Server 2014 that has databases with memory-optimized objects. When you restart SQL Server, it restarts successfully, and you may occasionally receive the following messages in the error log:
[ERROR] Unable to delete file <File Path>\<File Name>.dll for reason 5. File renamed to <File Path>\<File Name>.old_dll. This issue may be due to a previous failure to unload memory optimized table DLLs.