initiatedEventId

When the cause is WORKFLOW_ALREADY_RUNNING, initiatedEventId is the ID of the StartChildWorkflowExecutionInitiated event that corresponds to the StartChildWorkflowExecutionDecision to start the workflow execution. You can use this information to diagnose problems by tracing back the chain of events leading up to this event.

When the cause isn't WORKFLOW_ALREADY_RUNNING, initiatedEventId is set to 0 because the StartChildWorkflowExecutionInitiated event doesn't exist.