Why is an alternate Work Definition defined but still not being used despite resource overload?

Summary:

An item has two Work Definitions configured with the same Work Definition type but different resources and operations specific to each definition.

The bottleneck resource in both Work Definitions is configured as a non-24-hour resource and is flagged as a bottleneck resource. Although the primary Work Definition bottleneck resource is overloaded, the plan does not switch to the alternate Work Definition to fulfill demand.

Planning is being run as a Constrained Plan, with constraints applied to bottleneck resources only. The decision rules include:

• Use Alternate Resources
• Use Alternate Item Structures
• Use Alternate Work Definitions

Both Work Definitions are active, have no end date defined, and are assigned priorities 1 and 2 respectively.