A routine that determines if a device is ready to be used and, if it is, prepares a select instruction, channel command, and device order to accomplish an input/output activity or error recovery procedure.

• 一种程序,确定某个设备是否准备好被使用,如果是,则准备选择指令、通道命令和设备命令,以便完成一次输入输出操作或完成出错恢复过程。