METHOD FOR EFFICIENTLY SEARCHING FREE SPACE IN A RELATIONAL DATABASE

    公开(公告)号:CA2249080A1

    公开(公告)日:2000-03-25

    申请号:CA2249080

    申请日:1998-09-25

    Applicant: IBM CANADA

    Abstract: A method for efficiently searching free space in a relational database management system. The method limits the search to a finite number of space map pages in the free space map. If the configured number of space map pages in the free space map are searched and a page with free space is not found for the row, the row is inserted on the last page, or if no space is available on the last page a new page is created and the row is inserted on the new page. New rows are then appended until some predefined amount of space is filled before a search is done again. As a result, insertion of a row into the database management system does not incur the worst-case cost of searching the entire free space map.

    RESIZEABLE CACHE SENSITIVE HASH TABLE

    公开(公告)号:CA2384185A1

    公开(公告)日:2003-10-29

    申请号:CA2384185

    申请日:2002-04-29

    Applicant: IBM CANADA

    Abstract: A hash table is provided in which identifying properties of the data items pointed to by the hash table are selected and are included within the hash table buckets. The properties recorded in the buckets are able to be stored in a cache for the hash table and are used to located data items pointed to by the hash table. The hash table has bucket groups defining a second level hash table. The bucket groups are used to permit resizing of the hash table. Each bucket group has a latch so that that exclusive access for the resizing operation is obtainable on a group by group basis.

    SYSTEM AND METHOD FOR WARM SHUTDOWN AND RESTART OF A BUFFER POOL

    公开(公告)号:CA2433254A1

    公开(公告)日:2004-12-25

    申请号:CA2433254

    申请日:2003-06-25

    Applicant: IBM CANADA

    Abstract: A system and method for warm shutdown and restart of a buffer pool is provided. The buffer content including pages and control structures associated with these pages i s partitioned into blocks and each block is saved to disk as a sequential file. The size of eac h block may be selected to provide the optimal I/O (input/output) efficiency during buffer pool shutdown and restart operations. Blocks can be saved simultaneously using a number of writer threads. During restart of the buffer pool, the control information is read from the disk an d restored to the buffer pool using reader threads. The buffer pool may be made available for references to pages while reader threads are enabled to read the saved information by blocks to facilitate a more rapid restoration of information in the buffer pool. Allocation of portions of the buffer pool for restoring pages may be performed while the buffer pool is available for references to hasten availability.

    DYNAMIC SCALING BACK OF LATCH REQUESTS FOR COMPUTER SYSTEM RESOURCES

    公开(公告)号:CA2306969A1

    公开(公告)日:2001-10-28

    申请号:CA2306969

    申请日:2000-04-28

    Applicant: IBM CANADA

    Abstract: A computer system dynamically scales back latch requests for system resource s. Tasks seeking access to system resources each dynamically determine the probability that t he task will gain access to the latch relating to a given system resource. Where the task estimates that its probability is below a defined threshold, the task will suspend itself for a defined sleep time. The task dynamically adjusts the length of the sleep time based on the number of times the task enters the suspended state and on the relative changes in the estimated probability that the task will gain access to the resource.

    SYSTEM AND METHOD FOR STARTING A BUFFER POOL

    公开(公告)号:CA2438366A1

    公开(公告)日:2005-02-26

    申请号:CA2438366

    申请日:2003-08-26

    Applicant: IBM CANADA

    Abstract: For an information retrieval system coupled to a buffer pool maintaining a plurality of pages of recently accessed information for subsequent re-access , there is provided a method of starting the buffer pool. The method facilitates a quicker start to the buffer pool by deferring allocation of page storing portions, for example, until they ar e needed. The method comprises making the buffer pool available for storing pages while deferring allocation of a page storing portion of the buffer pool; and allocating the page storing portion of the buffer pool in response to a demand to store pages to the buffer pool . The method may be used to re-start a buffer pool with pages stored to a memory coupled to t he information retrieval system where the pages where stored upon a buffer pool shutdown. Further, buffer pool readers or prefetchers may be configured to read pages for storing to t he buffer pool and allocate the page storing portions of the buffer pool in response to instructions to read particular pages.

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