Abstract: A state of an input/output (I/O) operation in an I/O processing system is determined. A request for performing the I/O operation is received from an I/O operating system at a channel subsystem and forwarded to a control unit controlling an I/O device for executing the I/O operation. After a predetermined amount of time passes without receiving indication from the control unit that the I/O operation is completed, an interrogation request is received at the channel subsystem from the I/O operating system for determining the state of the I/O operation. An interrogation command is sent from the channel subsystem to the control unit. A response is received from the control unit, the response indicates a state of the I/O device executing the I/O operation, a state of the control unit controlling the I/O device executing the I/O operation, and the state of the I/O operation being executed.

Abstract: A computer program product, apparatus and method for processing a variable length device command word (DCW) at a control unit configured for communication with an input/output (I/O) subsystem in an I/O processing system. The computer program product includes a tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method. The method includes receiving a DCW at the control unit from the I/O subsystem. The DCW specifies one or more I/O operations and includes a command, a control data count, and control data having a varying length specified by the control data count. The control data is extracted in response to the control data count. The command is then executed in response to the extracted control data to perform the specified one or more I/O operations.

Abstract: Systems, methods and computer program products for providing indirect data addressing at an I/O subsystem of an I/O processing system. The computer program product includes a tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method. The method includes receiving a control word for an I/O operation. The control word includes an indirect data address for data associated with the I/O operation. The indirect data address includes a starting location of a list of storage addresses that collectively specify the data, the list spans two or more non-contiguous storage locations. Data is gathered responsive to the list. The gathered data is transmitted to a control unit in the I/O processing system.

Abstract: A computer program product, apparatus, and method are provided for determining a state of an input/output (I/O) operation in an I/O processing system. A request from a channel subsystem is received at a control unit for performing the I/O operation. After a predetermined amount of time passes without the I/O operation completing, an interrogation request is received from the channel subsystem at the control unit for determining the state of the I/O operation. A response is sent from the control unit to the channel subsystem indicating the state of the I/O operation in response to the interrogation request. The response also includes information regarding a state of an I/O device executing the I/O operation and information indicating a state of the control unit controlling the I/O device executing the I/O operation.

Abstract: A computer program product, apparatus, and method for handling exception condition feedback at a channel subsystem of an I/O processing system using data from a control unit are provided. The computer program product includes a tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method. The method includes sending a command message to the control unit, and receiving a response message in response to the command message. The response message includes exception condition feedback identifying a termination reason code in response to unsuccessful execution of at least one command in the command message. The method also includes interrupting a CPU in the I/O processing system, and reporting status associated with the exception condition feedback to the CPU in an interrupt response block.

Abstract: A method, system, program product and computer data structure for providing for two levels of server virtualization. A first hypervisor enables multiple logical partitions to share a set of resources and provides a first level of virtualization. A second hypervisor enables multiple, independent virtual machines to share the resources that are assigned to a single logical partition and provides a second level of virtualization. All events for all of the virtual machines within said single logical partition are grouped into a single partition-owned event queue for receiving event notifications from the shared resources for that single logical partition. A request for an interrupt is signaled for the grouped events from the partition-owned event queue for the demultiplexing of grouped events, by the machine, from the partition-owned event queue into individual, virtualized event queues that are allocated on a per virtual machine basis.