Within the toolbox there are a group of tools that help to control the direction and flow of the workflow.

What is the Existing Instance tool used for?

The existing instance tool is used to check if there is already an instance of this specific workflow running on the work item. This can be used to validate if the workflow has already been run, is currently in flight or has never been run previously. 

In some instances you may wish the behaviour of your workflow to alter if it has already been previously initiated.

Pre-Requisites

Work Item id - before using this command you will need to place the id of the workitem you want to verify into a variable. You can pass in either the work item the flow has been triggered from or another work item id if required.

Configuration