Host control of suspension and resumption of channel program execution

Claim 1

In an input/output device control mechanism responsive to a programmed input/output (I/O) instruction such as START I/O executed by a processor to obtain a channel address word (CAW) from a storage unit which provides the location in the storage unit for obtaining the first of a series of channel command words (CCWs) to be executed in sequence by a particular I/O device through a channel and a subchannel of the I/O device control mechanism, the improvement comprising: suspend means in said control mechanism for causing suspension of the execution of said series of CCW's and for disengaging said device from said channel at any CCW in said series containing a manifestation to so stop execution of said CCWs, said suspend means having disabling means for preventing the suspension in absence of an enabling manifestation in said CAW authorizing said suspension; and resume means in said control mechanism for causing the resumption of the execution of the series of CCWs at said any CCW at which a suspension occurs said resume means being responsive to a command to said I/O device control mechanism from said processor which command was generated by said processor in response to a programmed instruction to continue execution of said series of CCWs.