Refer to "Appendix G" – Upgrade and Patch Install Instructions of Diagnostics Installation and Configuration Guide.
A backup copy of the current Diagnostics Server directory (By default C:\MercuryDiagnostics\Server) must be taken before the upgrade or patch Install.
This is important for restoring, among other config files, alerts which are not stored in the Archive folder. They are dynamically generated, when alerts are created, as binary files with .mdt extension. They are stored in the "C:\MercuryDiagnostics\Server\storage\metadata\Default Client".
If Alerts are lost after an upgrade or patch installation, above mentioned files can be copied from backup and put in designated place.