Instance closing script is executed for every normally closed (by user action or deadline) workflow instances. This script may be useful for export process data to any external system.
When workflow is is terminated by administrator this script is not executed. Please use Instance Termination Script to handle termination events.
In script you can use $Instance to get or set initiated instance properties, $Initiator variable specifies the who is initiated workflow instance but variable can be null for module type tasks. You can also refer to right panel to list available scripting objects.
Unlike task prework or postwork scripts $Xml variable attached to data model root element, not the pool element.