A Windows client using the SMB protocol is trying to access a multiprotocol file system...

When a Windows client uses the SMB protocol to access a multiprotocol file system from a Dell Unity XT NAS server, the SID (Security Identifier) of the Windows user is mapped to a UID (User Identifier) on the UNIX file system. If no mapping is found in the local group database, the domain controller is checked to see if the SID is present there. The domain controller can provide the information needed to map the SID to the corresponding UID on the file system, allowing the Windows user to access the files. If the SID is not present in the domain controller, the Windows user's access would be removed.