Hitachi, Ltd.

Sadasaburo Kanai

Shoji Yamamoto

Kazuaki Tanaka

Takashi Sumiyoshi

Taro Inoue

Hidenori Umeno

Tetsuhiko Fujii

Yoshiaki Shinmura

Kazuo Imai

Toru Nishigaki

Kazuaki Masamoto

In a cache controller having a cache disposed between a CPU and a direct access storage for temporarily storing therein data transferred between the CPU and the storage, data is written from the cache into the storage in a write after mode. There is employed an update generation identifier specified by the CPU at each predetermined point of time. When storing data (write after data) from the cache into the storage in the write after mode, the last update generation specified prior to when the data is first written in the cache is set as the update generation of the data. When an update generation is specified by the CPU, write after data having a generation older than the specified generation by a predetermined effective management generation number n or more is preferentially written in the storage. When write after data is lost in the cache due to a failure during execution of a program, old data is read from the storage to execute again the program beginning from a point thereof corresponding to the oldest update generation of write after data, thereby recovering the lost write after data. Alternatively, the write after data is recovered by use of the update journals beginning from a point thereof associated with the oldest update generation.

Cache control method and cache controller

A cache mode selection method and system sets to a cache load inhibit mode a cache mode used for a random access dataset of lower access hit ratio if use ratio of a data transmission path exceeds beyond an upper use ratio limit. It also sets to the cache load inhibit mode the cache mode used by parts of a sequential access dataset. These make it possible to select a proper cache mode depending on state of a load dynamically to prevent an I/O response from decreasing so that the hit ratio can be increased.

Cache mode selection method for dynamically selecting a cache mode

A computer system including a plurality of shared resources to be used exclusively by a plurality of tasks. Upon occurrence of an interrupt, execution of the task running at that time is suspended to allow the interrupt task to be executed. After execution of the interrupt task, one of the tasks remaining in the execution waiting state is selected for execution. A method of scheduling tasks with priority to the task locking a shared resource includes the steps of registering a task identifier of a task being executed upon locking of the task to a resource, invalidating the registered identifier of the task when that task releases the shared resource from the locked state, deciding whether or not a valid task identifier representing the task which was running by locking the shared resource is registered when a task to be executed next is to be selected after execution of the interrupt task, and selecting the task designated by the task identifier, if registered, to thereby select the task as the one to be executed with priority.

Method of scheduling tasks with priority to interrupted task locking

There are provided a backup version page table in a storage for providing a correspondence between the pages of a database and the slots in a database storage medium in which the contents of pages to be recovered, if necessary, are stored; a current version page table for providing a correspondence between pages updated by a transaction and slots in the database storage medium wherein the updated contents of the pages are stored; and a journal file for recording various system journals; wherein the updated page contents are stored in the database stored medium at the slots not-used at that time and found with reference to the backup version page table and the current version page table. According to an aspect of another embodiment, there are provided a database constructed of a plurality of sub-areas; a differential file for each sub-area, and a backup file for each sub-area for copying the contents of each sub-area; wherein if the information in a certain sub-area of said database is updated, the updated information is stored in the differential file for the sub-area, and information is recovered using the backup file and the differential file for the certain sub-area.

Method and apparatus for database update/recovery

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Yokohama, Japan

Sadasaburo Kanai