https://docs.microsoft.com/en-us/sysinternals/downloads/psfile describes how to use the Psfiles and Psfiles64 programs.
- Log on to the gateway that you want to check for open files.
In the CONFIGURATION tab, select Main > Activity in the navigation pane.
The Activity Monitor page is displayed.
Run the Psfile or Psfile program using the Source IP value from the Activity Sessions section of the Activity Monitor page.
For example, psfiles64 \\192.168.91.89 -u admin -p password
where password is the gateway admin user password.
The program returns the open files on the remote gateway both with an ID for each open file and the path for the file.
- Rerun the Psfiles program using the -c flag with the ID or path of the files to forcibly close.