Sync failure due to open file handle

When sync server requires encryption (configured by the admin on the sync share), the client will attempt to enforce it by encrypting the root of the Work Folders and the staging folder. The Work Folders path is specified by the user, default path is “%userprofile%\Work Folders”. The staging folder is located at “%userprofile%\AppData\Local\Temp\WorkFoldersTemp”. If Work Folders path is not on the system drive, the staging folder will be a hidden folder on the drive where the Work Folders path is located.

If there are any open handles to the two paths, the policy enforcement will fail, and result in a sync failure. Sometimes, the error can be fixed by the user, such as closing the file explorer to the Work Folders path. Sometimes, the handle is opened by applications or system. You can check which application or process has the open handles to the paths by using the handles.exe ( The output gives you the PID of the process which holds the handle, and you will be able to find the process name from the task manager. Once the handle is closed, the user can click on “Sync now” to fix the sync error.


Anti-virus software should be deployed on both work folders server and user devices

There is no issue if anti-virus software is installed on both server and clients. As infected files will be detected on either endpoint, and get removed before it get synced.

If the anti-virus software is only installed on one sync endpoint (either on the server or on the client), there will undesired consequences when infected files are created on the endpoint which doesn’t have the anti-virus software installed.

For example, if the anti-virus software is installed on the server only, and an infected file is created on the client under the Work Folders. The infected file will be uploaded to the server, and removed by the anti-virus software on the server upon its detection. The sync process will find the file not uploaded to the server successfully, and continue to upload in the future, until the file is removed from the client.


Symbolic links or Junctions

Work Folders doesn’t support Symbolic links or junctions created under the Work Folders path. When a symlink or junction created, the sync will stop, and the following message will be shown to the user in the Work Folders Control panel: “A reparse point was detected and won’t be synced.” User can delete the symlink or the junction, sync will be able to continue.


Special considerations for PST files

PST files are generally large, while you can store PST files in Work Folders, but you need to be aware of the following:

  1. If an actively used PST file is placed under Work Folders path, Outlook has an open file handle, and Work Folders will skip it for sync.
  2. Depending on the latency, it can take a long time to sync the file. If the sync process was interrupted, the file will need to be re-synced from start.
  3. If the PST file is modified on multiple devices, and conflict was generated, it is hard to merge conflicts.


Data backup and restore on the server

In general, there are two approaches to backup and restore of the data on the server:

  1. Data only: The backup content will only store the users’ file data and upon restore, the restored files would be treated as “new” or “authoritative” versions of those files by the sync system and replicate the restored files to all endpoints. The SyncShare VssWriter is not required to be in these backup/restore paths.
  2. Application-consistent: During backup, the application VSS writer will be invoked, and create an application consistent backup, which includes not only the data but also the sync metadata. On restore, the files will be treated as “non-authoritative” copy, and get compared to the existing copy from other sync endpoints.