Overview
This article describes few means to find what process is currently accessing a certain file.Sometimes logging into the vault via M-Files Admin can fail because M-Files Server cannot open file MetaData.fdb. An example error below:
"Unspecified error. (I/O error for file "C:\Program Files\M-Files\Server Vaults\VaultName\MetaData\MetaData.fdb"
Error while trying to open file
The process cannot access the file because it is being used by another process. (ERROR: 335544344, SQLSTATE: 08001)) (0x80004005)
DBSession.cpp, 457, Database connection failed. (0x89790002)
Solution
You could open Resource Monitor (resmon.exe), open CPU tab and in the Associated Handles section add the string VaultName\MetaData\MetaData.fdb to the search box (adjust the string to match the file location in your case). In normal situation the process accessing MetaData.fdb should be MFServer.exe.Alternatively, you could try locating the process with Process Explorer (link below). Start it and press CTRL+F and search for string (adjust the string to match the file location in your case).
https://docs.microsoft.com/en-us/sysinternals/downloads/process-explorer
