Partial page write detection for a shared cache using a bit patt

Details Partial page write detection for a shared cache using a bit patt Partial page write detection for a shared cache using a bit patt

1992-10-01

1995-10-03

Black, Thomas G.

Boots, shoes, and leggings

395480, 3642434, 3642602, 3642653, 3642823, 3642854, 364DIG1, 36496427, 364DIG7, G06F 15167, G06F 1108

Patent

active

054559421

ABSTRACT:
Disk check bits refer to bit patterns stored in particular bytes of a page which are used to detect errors in writing the page to storage. Every time a page is obtained from storage, changed from the version retained in storage, and written back to storage, the check bit pattern on the changed page is altered to be different from the bit pattern on the storage page. This is because the changed page overwrites the stored page. The invention provides a method for managing the check bits in a multi-DBMS system employing a high-speed shared electronic store as a store-in cache for all pages obtained from disk storage. When a page is first obtained from disk storage by a DBMS and changed, check bit information for the page is maintained in a directory of the storing cache which indicates what the patterns are for the version of the page in the disk storage. All pages which are modified are stored in the store-in cache and are only returned to disk storage from the cache. Therefore, when a page is to be written to disk storage, the DBMS writing the page to storage processes the check bits on the page itself, changing them as required based on the check bit information stored in the directory for the page.

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Crus, et al., "Partial Data Page Write Detection" Technical Disclosure Bulletin, IBM, Apr. 1983 vol. 25, No. 11B.
Partial Data Page Write Detection. Apr. 1983-Crus et al-Technical Disclosure Bulletin, Apr. 1983, p. 5889.

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