Explanation
Some effects of parking a purchase order are:
You can use Situation Handling to alert users about incomplete documents, which means that you can notify the responsible users or approvers about the parked purchase orders that need their attention or action.
You can use a workflow to request completion of the document, which means that you can automate and streamline the process of completing and releasing the parked purchase orders by using predefined rules and conditions. References: SAP S/4HANA Sourcing and Procurement | SAP Learning, Course S4520, Unit 1, Lesson 1.