Hi there,

We have two separate unrelated sites deployed to Azure.

One is on Umbraco 8.6.0 and the other is Umbraco 8.6.4.

Both sites are just single sites, no load balancing etc.

Both have followed this guide: https://our.umbraco.com/documentation/Getting-Started/Setup/Server-Setup/azure-web-apps

and both have the same settings that should solve this issue:

Boot failed: Umbraco cannot run. See Umbraco's log file for more details.

-> Umbraco.Core.Exceptions.BootFailedException: Boot failed.

-> System.IO.IOException: The process cannot access the file 'C:\home\site\wwwroot\App_Data\TEMP\NuCache\NuCache.Content.db' because it is being used by another process.
  at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
  at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost)
  at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options)
  at CSharpTest.Net.IO.TransactedCompoundFile..ctor(Options options)
  at CSharpTest.Net.Storage.BTreeFileStoreV2..ctor(Options options)
  at CSharpTest.Net.Collections.BPlusTree`2.OptionsV2.CreateStorage()
  at CSharpTest.Net.Collections.BPlusTree`2.NodeCacheBase..ctor(BPlusTreeOptions`2 options)
  at CSharpTest.Net.Collections.BPlusTree`2.NodeCacheNone..ctor(BPlusTreeOptions`2 options)
  at CSharpTest.Net.Collections.BPlusTree`2..ctor(BPlusTreeOptions`2 ioptions)
  at Umbraco.Web.PublishedCache.NuCache.DataSource.BTree.GetTree(String filepath, Boolean exists) in D:\a\1\s\src\Umbraco.Web\PublishedCache\NuCache\DataSource\BTree.cs:line 27
  at Umbraco.Web.PublishedCache.NuCache.PublishedSnapshotService.MainDomRegister() in ....

This problem has only occurred on 8.6.4, not on 8.6.0.

8.6.4 possibly has regressed this issue in some way.

We didn't have WEBSITEDISABLEOVERLAPPED_RECYCLING = 1 set on either site, but we've now set it on the 8.6.4 site to see if that stops the issue from happening.

It is not frequent - say once every 6-8 weeks.

Are we missing anything here? I notice that there were some changes to the SqlMainDomLock in 8.6.4 release notes

https://github.com/umbraco/Umbraco-CMS/issues/8398