If you are performing Incremental Parallel Upgrades from OnBase 12 or earlier, it is recommended that you deploy two separate Application Servers: one Application Server running Microsoft .NET Framework 4.0 for OnBase 12 or earlier, and one Application Server running a currently supported version of Microsoft .NET Framework for OnBase Foundation 22.1. This will help you to avoid compatibility issues with different versions of Microsoft .NET Framework while performing the upgrade.