Each workflow run has a unique run ID. $PMWorkflowRunId returns the workflow run ID as a string value. Use $PMWorkflowRunId with any function that accepts string datatypes.
Use $PMWorkflowRunId in a mapping, a mapplet, workflow links, or in workflow tasks such as Assignment and Decision tasks. You can also use $PMWorkflowRunId in input fields that accept mapping or workflow variables. For example, you configure a workflow to run concurrently with the same instance name, and you want to track the status of each workflow run using a third-party application. Use $PMWorkflowRunId in a post-session shell command to pass the run ID to the application.