Abstract: Disclosed are a method and system for parallel execution of recovery in a non-homogeneous multi-processor environment. The method defines criteria how to decide which recovery actions are to be performed, and on which processor. If multiple recovery actions are pending, the goal is to execute them in parallel on multiple processors. This is much more efficient than the traditional approach of one processor doing all the required recovery. In addition, in large, non-homogeneous systems such a single processor capable of doing the complete recovery might not be existing at all due to technical limitations. The method of this invention also defines rules and mechanisms how multiple processors executing recovery in parallel can access shared resources while avoiding deadlock situations. This includes accessing resources that are currently owned by another processor.

Abstract: A bi-directional and full duplex facility for permitting both the IO processor and the Channel to write CCA messages on their respective queues at the same time. IOP messages to the channel are stored on the TO_CHN queue and Channel messages to the IOP on the TO_IOP queue. CCA Queues replace hardware CCAs due to increasing transmission capabilities of current IO processors and Channel processors. Even though the mechanism is similar, the present invention provides some benefits in the use of signaling. The IOP does not have to signal the Channel each time it puts something on its outbound queue. Each queue contains multiple slots. This allows the IOP and Channel to write multiple messages on the targeted queue without encountering a CCA busy signal. The actual queues are now structured in hardware system memory.

Abstract: Disclosed are a method and system for detecting errors in a computer system including a processing unit to perform tasks to change items. The method comprises the steps of assigning a task control block to the processing unit, and using the task control block to keep track of items being changed by the processing unit. The method comprises the further steps of at defined times, checking the task control block to identify items being changed by the processing unit, and checking the states of said identified items to determine if those states are correct. The preferred embodiment of the invention detects an error when it arises (where possible), and utilizes an infrastructure that allows simple and periodic consistency checks (for example, at designated code points) that detect the error before it causes follow-on problems.

Abstract: An input/output subsystem is configured as a plurality of input/output subsystem images, each of which appears to a program as an independent input/output subsystem. An input/output subsystem image is identified by an input/output subsystem image identifier, which is used by various programs to designate the particular input/output subsystem image for which an I/O operation is to be performed. An input/output subsystem image includes, for instance, one or more input/output paths. An input/output path of an input/output subsystem image is identified by an input/output path identifier, as well as a physical input/output path identifier.

Abstract: A bi-directional and full duplex facility for permitting both the IO processor and the Channel to write CCA messages on their respective queues at the same time. IOP messages to the channel are stored on the TO_CHN queue and Channel messages to the IOP on the TO_IOP queue. CCA Queues replace hardware CCAs due to increasing transmission capabilities of current IO processors and Channel processors. Even though the mechanism is similar, the present invention provides some benefits in the use of signaling. The IOP does not have to signal the Channel each time it puts something on its outbound queue. Each queue contains multiple slots. This allows the IOP and Channel to write multiple messages on the targeted queue without encountering a CCA busy signal. The actual queues are now structured in hardware system memory.

Abstract: Operations in a multi-processor, multi-control block environment are timed u sing timing queues and instruction queues. Upon receipt of a request for a subchannel control block (SCB) to perform an operation that needs to be timed, the SCB is queued on one of multiple timing queues based on an elapsed timeout limit (ETL) of the operation. There is an ETL for each operation, and each one the multiple timing queues is associated with an ETL for completing an operation. The SCB may be placed at the bottom of the timing queue, the timing queue ordered from oldest to youngest which allows for quickly checking large numbers of SCBs without having to check every element queue and without having to dequeuing the elements from this queue. Upon receipt of a request to perform a high-priority operation, the SCB may be queued in a high priority instruction queue. The SCB may remain the timing queue to retain its order and be placed on a high priority instruction queue for retrying an operation.

Abstract: An Input/output (I/O) measurement block facility is provided that creates subchannel measurement blocks (comprising device busy values) related to performance of an I/O operation of a subchannel, wherein a device busy time value is a sum of time intervals when the subchannel is device busy during an attempt to initiate any one of a start function or a resume function at the subchannel.

Abstract: An input/output subsystem is configured as a plurality of input/output subsystem images, each of which appears to a program as an independent input/output subsystem. An input/output subsystem image is identified by an input/output subsystem image identifier, which is used by various programs to designate the particular input/output subsystem image for which an I/O operation is to be performed. An input/output subsystem image includes, for instance, one or more input/output paths. An input/output path of an input/output subsystem image is identified by an input/output path identifier, as well as a physical input/output path identifier.

Abstract: A communications adapter is shared by a plurality of input/output (I/O) subsystem images of an I/O subsystem of a central processing complex. To enable the sharing, the communications adapter is configured to a plurality of I/O paths of the plurality of I/O subsystem images. An I/O subsystem may have one or more shared communications adapters.

Abstract: I/O measurement data associated with the performance of an I/O operation process is gathered during the I/O process. The I/O measurement data is saved in an IRB memory location specified by a test subchannel instruction. An I/O interrupt signals the completion of the I/O operation process.

Abstract: An input/output subsystem of a computing environment is configured as a plurality of input/output subsystem images, each of which appears to a program as an independent input/output subsystem. An input/output subsystem image includes one or more communications adapters used for communicating within the computing environment. A communications adapter is identified by hardware of the computing environment by using a first identifier, and it is identified by a program of the computing environment by using a second identifier. The identifiers can be of different sizes.

Abstract: Input/output (I/O) measurement facilities are provided. An extended I/O measurement block facility is provided that enables measurement blocks to be stored in discontiguous areas of main storage and to be accessed directly via addresses. In a further aspect, an extended I/O measurement word facility is provided that facilitates the obtaining of measurement data for single I/O operations.

Abstract: An apparatus, method and program product for selecting paths between a main memory and I/O devices in a data processing system having a main memory for storing data, one or more I/O devices for receiving data from or sending data to the main memory, and an I/O processor (IOP) for controlling I/O operations for sending data between the main memory and the I/O devices. The data processing system includes disparate channels between the IOP and the I/O devices. The disparate channels carry data between the main memory and the I/O devices during the I/O operations. Included is a computer program executed by the IOP for assigning a path weight to selected ones of the disparate channel paths to be used in selecting the next channel path to carry data between the main memory and I/O devices. Each disparate channel type has a different set of criteria for evaluating the path weight.

Abstract: A communications adapter is shared by a plurality of input/output (I/O) subsystem images of an I/O subsystem of a central processing complex. To enable the sharing, the communications adapter is configured to a plurality of I/O paths of the plurality of I/O subsystem images. An I/O subsystem may have one or more shared communications adapters.

Abstract: Input/output (I/O) measurement facilities are provided. An extended I/O measurement block facility is provided that enables measurement blocks to be stored in discontiguous areas of main storage and to be accessed directly via addresses. In a further aspect, an extended I/O measurement word facility is provided that facilitates the obtaining of measurement data for single I/O operations.

Abstract: An input/output subsystem of a computing environment is configured as a plurality of input/output subsystem images, each of which appears to a program as an independent input/output subsystem. An input/output subsystem image includes one or more communications adapters used for communicating within the computing environment. A communications adapter is identified by hardware of the computing environment by using a first identifier, and it is identified by a program of the computing environment by using a second identifier. The identifiers can be of different sizes.

Abstract: An input/output subsystem is configured as a plurality of input/output subsystem images, each of which appears to a program as an independent input/output subsystem. An input/output subsystem image is identified by an input/output subsystem image identifier, which is used by various programs to designate the particular input/output subsystem image for which an I/O operation is to be performed. An input/output subsystem image includes, for instance, one or more input/output paths. An input/output path of an input/output subsystem image is identified by an input/output path identifier, as well as a physical input/output path identifier.

Abstract: An apparatus, method and program product for selecting paths between a main memory and I/O devices in a data processing system having a main memory for storing data, one or more I/O devices for receiving data from or sending data to the main memory, and an I/O processor (IOP) for controlling I/O operations for sending data between the main memory and the I/O devices. The data processing system includes disparate channels between the IOP and the I/O devices. The disparate channels carry data between the main memory and the I/O devices during the I/O operations. Included is a computer program executed by the IOP for assigning a path weight to selected ones of the disparate channel paths to be used in selecting the next channel path to carry data between the main memory and I/O devices. Each disparate channel type has a different set of criteria for evaluating the path weight.