The diagnostic determines which cloud IaaS products, network components, and virtualization machines are needed for an application. It addresses the platform components (server/operating system and web server) in the PaaS layer. It focuses on the SaaS software application. Simple ports (different version of virtualization software or later release of an operating system) can occur as long as they do not impact the software running in the SAAS layer. The diagnostic helps determine what functionality was required for input into a SLA (Service Level Agreement)”]
Source: https://www.csoonline.com/article/2129233/creating-a-cloud-sla-from-diagnostic-data.html