Cancels a pending step or steps in a running cluster. Available only in Amazon EMR versions 4.8.0 and later, excluding version 5.0.0. A maximum of 256 steps are allowed in each CancelSteps request. CancelSteps is idempotent but asynchronous; it does not guarantee that a step will be canceled, even if the request is successfully submitted. When you use Amazon EMR releases 5.28.0 and later, you can cancel steps that are in a <code>PENDING</code> or <code>RUNNING</code> state. In earlier versions of Amazon EMR, you can only cancel steps that are in a <code>PENDING</code> state.