Environment Setup for Congestion Analysis

Note the following settings to perform congestion analysis.

The Congestion Analysis assistant is available in Layout EXL and higher tiers.
Ensure that Default Wire Constraint Group is set to LEFDefaultRouteSpec. This is required because the global router requires a default constraint group where both validRoutingLayers and validRoutingVias constraints are set.
Ensure that Design Style in the Virtuoso Space-based Router form is either selected as Chip Assembly or ASIC. Congestion Analysis has limited functionality when Design Style is set to Device.
Ensure that the Route Flow in the Wire Assistant is selected as Minimum Spanning Tree. Congestion analysis only supports the Minimum Span Tree routing flow.