Method and apparatus for managing coherency in object and page caches
First Claim
1. A database management apparatus comprising:
- a page cache to store a page having a fixed length containing an object read from a database storing the object;
an object cache that stores the object read from the page stored in the page cache;
a page status information storage device to store page cache status information indicating whether the page stored in the page cache and the page on the database corresponding to the page are consistent;
an object status information storage device to store object cache status information indicating whether the object stored in the object cache and the object on the database corresponding to the object are consistent; and
a status information synchronizing device to execute a synchronization process in order to make the page cache status information stored in the page status storing device corresponding to the page stored in the page cache consistent with the object cache status information stored in the object status information storage device corresponding to the object that is read from the page and stored in the object cache, wherein the status information synchronizing device comprises;
a database determination device to determine whether the page to be stored in the page cache containing the object for which the access request is received consistent with the page in the database corresponding to the pages anda status information updating device that sets the page status information of the page to invalid status indicating inconsistency with the database when the database determination device determines inconsistency and sets the object status information that is stored in the object status information storage device corresponding to the object read from the page and stored in the object cache to the invalid status that is a status not guaranteeing consistency with the corresponding object in the database.
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Accused Products
Abstract
To reduce process time by simplifying the cache status and to improve the execution efficiency of the application program in the separate region conversion system that is capable of maintaining the hit rate of the cache at high level. When an access request is made to the object and if the object is not stored in the object cache, the page containing the object is read from the database and is stored in the page cache, and the object is read from the page and stored in the cache. The status of the page cache describing the status of the page stored in the page cache is stored in the page status storage device and at the same time the status of the object cache describing the status of the object stored in the object cache is stored in the object status storage device. By establishing a relationship between the status of the page cache and the status of the object, if the status of the page cache and the corresponding status of the object cache are not consistent, the status synchronizing device executes a synchronization process to make these status consistent.
166 Citations
15 Claims
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1. A database management apparatus comprising:
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a page cache to store a page having a fixed length containing an object read from a database storing the object; an object cache that stores the object read from the page stored in the page cache; a page status information storage device to store page cache status information indicating whether the page stored in the page cache and the page on the database corresponding to the page are consistent; an object status information storage device to store object cache status information indicating whether the object stored in the object cache and the object on the database corresponding to the object are consistent; and a status information synchronizing device to execute a synchronization process in order to make the page cache status information stored in the page status storing device corresponding to the page stored in the page cache consistent with the object cache status information stored in the object status information storage device corresponding to the object that is read from the page and stored in the object cache, wherein the status information synchronizing device comprises; a database determination device to determine whether the page to be stored in the page cache containing the object for which the access request is received consistent with the page in the database corresponding to the pages and a status information updating device that sets the page status information of the page to invalid status indicating inconsistency with the database when the database determination device determines inconsistency and sets the object status information that is stored in the object status information storage device corresponding to the object read from the page and stored in the object cache to the invalid status that is a status not guaranteeing consistency with the corresponding object in the database. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A database management apparatus comprising:
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a database reading device to read a page that includes data of a fixed length containing the object for which the access request is received from a database in response to the access request to the object stored in the database that stores the object; a page cache to store the page read by the database reading device; a page cache reading device to read the object for which the access request is received from the page stored in the page cache; an object cache to store the object read by the page cache reading device; a page status information storage device to store the page status information indicating whether the page stored in the page cache is consistent with the page in the database corresponding to the page; an object status information storage device to store the object status information indicating whether the object stored in the object cache is consistent with the object in the database corresponding to the object, and a status information synchronizing device to execute a synchronization process that makes the page status information stored in the page status information storage device corresponding to the page stored in the page cache consistent with the object status information stored in the object status information storage device corresponding to the object read from the page and stored in the object cache, wherein the status information synchronizing device comprises; a database determination device to determine whether the page to be stored in the page cache containing the object for which the access request is received consistent with the page in the database corresponding to the page, and a status information updating device that sets the pare status information of the page to invalid status indicating inconsistency with the database when the database determination device determines inconsistency and sets the object status information that is stored in the object status information storage device corresponding to the object read from the page and stored in the object cache to the invalid status that is a status not guaranteeing consistency with the corresponding object in the database. - View Dependent Claims (8)
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9. A database management method to be applied to a database management apparatus having a page cache to store a page that comprises data of a fixed length containing an object read from the database that stores the object and an object cache to store the object read from the page cache, the method comprising the steps of:
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receiving an access request for the object in the database; determining whether the page in the page cache containing the object for which the access request is received is consistent with the page in the database corresponding to the page; declaring the page in the page cache invalid in the case of inconsistency; declaring the object read from the page in the object cache invalid; reading the page in the database containing the object for which the access request is received to write to the page cache; declaring the page in the page cache valid; reading the object for which the access request is received from the page on the page cache; converting the read object to the object in computable format; storing the object in the computable format to the object cache; and declaring the stored object in the object cache valid.
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10. A database management apparatus comprising:
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page cache means for storing a page having a fixed length containing an object read from a database storing the object; object cache means for storing the object read from the page stored in the page cache means; page status information storage means for storing page cache status information indicating whether the page stored in the page cache means and the page on the database corresponding to the page are consistent; object status information storage mans for storing object cache status information indicating whether the object stored in the object cache means and the object in the database corresponding to the object are consistent; and status information synchronizing means for executing a synchronization process to make the page cache status information stored in the page status storing means corresponding to the page stored in the page cache means consistent with the object cache status information stored in the object status information storage means corresponding to the object that is read from the page and stored in the object cache means, wherein the status information synchronizing means comprises; database determination means for determining whether the page to be stored in the page cache means containing the object for which the access request is received consistent with the page in the database corresponding to the page, and status information updating means for setting the page status information of the page to be invalid status indicating inconsistency with the database when the database determination means determines inconsistency and sets the object status information that is stored in the object status information storage means corresponding to the object read from the page and stored in the object cache means to the invalid status that is a status not guaranteeing consistency with the corresponding object in the database. - View Dependent Claims (11, 12, 13, 14, 15)
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Specification