Abstract: The invention provides that each of the components (i.e., switches, LAN segments, and workstations) is treated as a node for placement in a tree structure topology, with one switch at the top of the tree. Each switch may have other switches or LAN segments connected to it, with each LAN segment having a plurality of workstations attached to it. The workstations are the leaf nodes of the tree and cannot have anything connected to them. The inventive method for determining optimal partitioning is to calculate the mean switch delay, the mean segment delay, and the standard deviation as a function of the total number of workstations in the network, and to sum the values together. Finally, the invention applies a Tabu Search to the potential tree-structured solutions to the problem in order to rapidly and accurately determine the optimal network configuration.

Abstract: A method and system for managing one or more coupling facilities in a data processing system. An active policy is used to control resources located in the coupling facilities. The active policy can be changed such that control of the resources can be altered. Compatible changes are made immediately and incompatible changes are made at a subsequent time. Recorded in the active policy and in the coupling facilities is information regarding the resources. When the information in the active policy is not in synchronization with the information in the coupling facilities, a reconciliation technique is performed. The resources in the coupling facilities can be modified but prior to the modification, the intended modifications are stored in the active policy.

Abstract: Execution of input/output operations is controlled by one or more suspend and/or resume mechanisms. Suspension of an input/output operation is accomplished by one of a number of mechanisms including, for instance, a START SUBCHANNEL instruction with execution limits, a SUSPEND SUBCHANNEL instruction with or without a suspension time limit, or a suspend subchannel channel command word with or without a suspension time limit. Subsequent to suspending execution of a channel program, execution can be resumed automatically or by issuing a RESUME SUBCHANNEL instruction with limits or a resume subchannel channel command word with limits.

Abstract: A data processing system operating under a multiprocessing hypervisor program subject to I/O interrupts during a polling interval of the hypervisor program includes one or more processors for executing the hypervisor program and host system and one or more guest systems under the hypervisor program, a storage system connected to the processor's by a bus for storing instructions, data and control information associated with the systems being executed by the processor, the storage system may be partitioned into a number of separate areas each associated with one of the concurrently operating systems, an input/output subsystem for generating I/O interrupts to the processors, apparatus for testing to determine if the system is operating in an interpretive execution mode, apparatus for determining whether a dedicated region facility is active, apparatus for testing whether an I/O enablement mask for a guest system has been set, apparatus for setting a flag if the guest system I/O enablement mask is set, apparatus

Abstract: Disclosed is a data processing system for presenting concurrent requests for access to peripheral devices up to the number of subchannels available for handling input/output operations. A computer system provides a plurality of subchannels and affiliated unit control blocks for input/output operations between main storage and the peripheral devices. The unit control blocks comprise two groups, including a first dedicated to the peripheral devices and a second group available for dynamic association with the peripheral devices on a demand basis. The unit control blocks are termed base unit control blocks and alias unit control blocks, respectively. Upon system initialization, alias unit control blocks for a given logical subsystem are linked in a free pool. To initiate an input/output operation a program executing on the CPU first queries a base unit control block for a target peripheral device to determine its availability.

Abstract: A method and system for rebuilding storage structures located within one or more structure processing facilities of a data processing system. A connection is made to a first storage structure having a name and one or more predefined characteristics. Thereafter, a second storage structure is allocated having the same name as the first structure, however, one or more of the predefined characteristics of the second structure are different than the predefined characteristics of the first structure. The second structure may be used for planned system reconfigurations or for recovery from system failures. During the rebuilding process, notification of phases of the rebuilding process are given to the active users. Further, a capability is provided for terminating the rebuilding process. In addition, a method and system for coordinating phases of user defined processing is provided.

Abstract: A method and system for managing information in a data processing system is provided. The data processing system includes one or more operating systems coupled to a coupling facility. Stored within the coupling facility is data, which is accessed by one or more users. The status of those users are also stored in the coupling facility. A number of operating system services are provided for recording the users' status and managing the data and the users of the data. The data may include cache, list and/or lock structures.

Abstract: A data processing system, having virtual addressing capability, has a real storage manager to associate virtual storage locations with real storage by accessing page tables to determine the locations of "backed" virtual storage pages in central, expanded, or auxiliary storage. The real storage manager accepts requests to copy ranges of virtual storage from one virtual storage range to another, and, in so doing, uses the page tables to effectively perform the copying by reassigning backed pages from the source range to the target range. Having been reassigned to the target range, the backed pages are artificially aged by increasing the unreferenced interval count (UIC), so that the backed pages in the target range will be likely candidates for page stealing.