<p>The <code>clientToken</code> parameter is an idempotency token. It ensures that your <code>UpdateFlow</code> request completes only once. You choose the value to pass. For example, if you don't receive a response from your request, you can safely retry the request with the same <code>clientToken</code> parameter value.</p> <p>If you omit a <code>clientToken</code> value, the Amazon Web Services SDK that you are using inserts a value for you. This way, the SDK can safely retry requests multiple times after a network error. You must provide your own value for other use cases.</p> <p>If you specify input parameters that differ from your first request, an error occurs. If you use a different value for <code>clientToken</code>, Amazon AppFlow considers it a new call to <code>UpdateFlow</code>. The token is active for 8 hours.</p>