1.4.3. Use Clock Region Assignments to Optimize Clock Constraints
Clock Region assignments allow you to control the placement of the clock region for floorplanning reasons. For example, use a Clock Region assignment to ensure that a certain area of the device has access to a global signal, throughout your design iterations. A Clock Region assignment can also be used in cases of congestion involving global signal resources. By specifying a smaller clock region size, the assignment prevents a signal using spine clock resources in the excluded sectors that may be encountering clock-related congestion.
You can specify Clock Region assignments in the assignment editor.