In SNA,a request unit sent only in reaction to a received request unit; for example,Quiesce Complete is the reply sent after receipt of Quiesce At End of Chain.

• 在系统网络体系结构（SNA）中，仅对接受的请求单元进行反馈时发送的一种请求单元。例如，在接受了“链结束停顿”后发送“停顿完成”应答。