There is provided, in accordance with the present invention, apparatus comprising a shared random access memory in which is stored requests for access to data in a bulk memory unit. The data being stored in redundant storage areas and the requests stored in the RAM include the address of the redundant data. Means are provided for determining if that data request is already in progress through one of the redundant addresses. The first of the addresses accessed causes the others to be blocked to prevent multiple accessing of the same data. The checking and selection is accomplished by high speed logic circuitry.
The disclosure provides a unique multiprocessing (MP) method for executing on plural CPUs of the MP a uniprocessor system (UPS) program not written to run on a MP system. Separate copies of the UPS are provided in the shared main storage (MS) of the MP. A hypervisor type of control program (called a partitioned multiprocessing system, PMP) uses the MP method to enable simultaneous execution of the plural copies of a UPS on different CPUs of the MP as UPS guest virtual machines. PMP can dedicate any CPU to the sole execution of a particular copy of UPS. The copies of the UPS run on the different CPUs independently of each other, but they may share I/O devices.
A system and method for piggybacking read responses on a shared memory, multiprocessor bus having a plurality of nodes coupled to the bus. The system determines whether a pending read request from a first node targets data required by a subsequent read request from a second node. The system then piggybacks a read response corresponding to the pending read request by permitting the first and second nodes to share the required data without transmitting the subsequent read request on the bus or otherwise generating any additional bus traffic. The system also supports piggybacking of multiple simultaneous read transactions to different addresses.
The present invention offers an improved type of shared memory area management system for use in a network system which includes a main computer accessed through a plurality of terminals and a memory area provided in said main computer the use of which is shared by said terminals, wherein the memory area is divided into a plurality of delimited areas, and wherein are provided a first bit map and a second bit map each including a plurality of flag areas corresponding to the delimited areas and adapted to show the state of shared use of the areas in such a manner that, when it is necessary to reserve or release any one of the delimited areas for processing a task by way of any one of the terminals, the state of a corresponding flag area in the first bit map may be changed, and that when such task in the delimited area is determined to be completed, the state of corresponding flag area in the second bit map may be changed accordingly.
A data storage system with data mirroring and reduced access time data retrieval includes at least one pair of rotating data storage media each having a plurality of generally identical data records. Each rotating data storage medium includes position indicators, for providing one or more indications of the rotational position of each of the rotating data storage media with respect to its associated fixed position read/write mechanism. A position monitor receives the rotational position indications from each rotating data storage medium and computes and monitors the rotational position of each rotating storage medium with respect to its associated read/write mechanism. After receiving a request for access to one or more data records stored on the pair of rotating data storage media, the system computes projected data access times for retrieving the requested data record on each of the rotating data storage media, and commands retrieval of the requested data record to the rotating data storage medium having the shortest projected data access time based on the rotational position and state of the respective data storage medium.
An exclusive control system is provided in a system having a memory module and a plurality of processing modules sharing the memory module, each of the plurality of processing modules exclusively accessing the memory module while prohibiting other processing modules from accessing the memory module. The exclusive control system includes a determination unit for determining whether or not a process executed in response to an access request from a processor module among the plurality of processing modules is normally completed in the memory module, and a retry unit for, when the determination unit determines that the process executed in response to the access request is not normally completed, retrying the process while maintaining a state in which other processing modules are prohibited from accessing the memory module.
