How to: Manage NSS Snapshot files


The purpose of this article is to explain the concept of NSS snapshot files and where they can be found. The article also shows a number of possible rare scenarios where Snapshot files may cause strange behaviors or interfere with NSS operations.

What are NSS Snapshot Files?

Snapshot files are created when a Host Scan is being run. These files will allow the Host Scan to proceed from a certain stage if the NSS service is stopped. Snapshot files are saved every 5 minutes for host scans. For file-level reports Snapshots can be created more often. In short, the snapshot files act as checkpoints from which scans can resume.

The disrupted scans will resume when the NSS Core service restarts. The NSS Core Service will look for existing snapshot files upon starting and it will attempt to resume the scans tied to the files. Scans that were stopped with the 'Abort'-button in the NSS Host Management interface will not resume after a service restart.

Snapshot files are by default stored in the service account’s temp folder (in the Northern subfolder). By default, this directory can be found at C:\Users\service_account\AppData\Local\Temp\Northern\ (where service_account is the name of your NSS Service Account). When a Host Scan is finished, all Snapshot files related to that scan are automatically removed.

It is possible to change where the Snapshot files are stored by altering the value of a certain parameter in the Windows registry.

How to change the Snapshot file location:

  1. Stop the NSS Core Server service.
  2. Open up the Windows Registry on the NSS Server as an administrator and go to HKEY_LOCAL_MACHINE\SOFTWARE\Northern\Settings  
  3. Find the parameter named NSS::TempFolder at the end of the parameter list and double click it.
  4. Set the parameter value to your desired path (e.g. C:\NSS\Snapshots) and click on OK
  5. Start the NSS Core server service

Deleting NSS Snapshot Files

As mentioned in the previous section, snapshot files are automatically removed when the Host Scan is completed. However, on very rare occasions this deletion may fail. This situation may occur if the NSS Core service terminates unexpectedly or the NSS host server itself crashes.

If redundant snapshot files are not deleted as expected (a scan is finished, but snapshot files remain) the NSS Core service will attempt to restart scans that are already finished.

In rare circumstances partial deletion of snapshot files may occur, leaving corrupt Snapshots. Corrupted snapshot files are typically very large in size and they could cause serious issues to the Northern Storage Suite environment. These files contain data that cannot be processed properly by NSS and one common result of this is rapid memory consumption growth which eventually could result in a NSS Core service crash.

Snapshot files that have not been deleted by NSS as expected, should be removed immediately.

How to remove Snapshot files:

  1. Stop the NSS Core Server service.
  2. Navigate to C:\Users\service_account\AppData\Local\Temp\Northern\ (or your customized path configured in NSS::TempFolder)
  3. Select all files and folders in this directory and delete them.
  4. Start the NSS Core Server service.

Example of an unusually large snapshot file:

Large snapshot file

Confirm results

Make sure that the NSS Core Server service is started and run a new Host Scan to verify that;

  1. That Snapshot files are stored to the new location during the scan (if you have changed the default location following the procedure above).
  2. That the Snapshot-related error has been solved (after removing old and/or corrupted snapshot files).

For advanced troubleshooting, please contact the Technical Support team at Northern (

KB Article: 3114

Updated: 1/28/2016

  • Category
    • Usage
  • Affected versions
    • NSS 9.5
    • NSS 9.6

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