Command retry control by peripheral devices

摘要: An input/output subsystem in which a peripheral device controller controls the response to commands received from an (I/O) channel. A sequence of channel command words (CCWs) are stored sequential addresses main memory. Some CCWs contain commands, other memory for data but no commands. initial instruction gives address where first CCW is The location last containing retained back-up register Further chained provide scattered storage blocks data. At completion transfer operation associated with CCW, incremented by one thereby specify next and hence, CCW. contains at further be stored. occurrence signal I/O indicating error or nonerror condition, either conditions require retrying original command, causes utilize fetch control work command. This provides way backing up program without interrupting computer retry initializing even though intervening were executed.