Page refreshing procedure using two locking granularities to ensure cache coherency in a multisystem database processing environment having a high-speed shared electronic store
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United States of America Patent
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Aug 13, 1996
Grant Date -
N/A
app pub date -
May 2, 1994
filing date -
May 2, 1994
priority date (Note) -
Expired
status (Latency Note)
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Abstract
A method for ensuring data coherence while detecting whether the locally cached copy of a data page is invalid and responsively refreshing the locally cached page from a Shared Electronic Store (SES) in a multisystem shared disk environment. Locally cached data pages may become invalid in a multisystem shared disk environment because of transactions executed by other systems for the common database. Thus, whenever a transaction in a database management system (DBMS) instance desires to read or update a record in a locally cached data page, the DBMS must first verify validity for the locally cached copy and, for stale or invalid copies, must re-read and re-register the latest version in the SES. This invention provides a procedure for the necessary verification and refreshing steps that relies on page latching to serialize the combination of local multiuser and global multisystem activities. The procedure of this invention supports both record and page locking granularities.
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