The defining characteristic of version 5.6.3 is how it handles traditional server services. This version began the process of services from new installations to signal their upcoming removal. Feature Type Status in 5.6.3
This version is the ultimate release for macOS High Sierra 10.13.6 . macOS Server 5.6.3
As a legacy version, 5.6.3 has developed several significant maintenance challenges for those still running it: The defining characteristic of version 5