| 摘要 |
A SQL database server system having an enhanced logging system is described. The logging system implements a "private log cache" (PLC) for reducing the contention on the system's "log" resource (which is protected by a log semaphore). An area of memory private to a user's task is set aside as a PLC-a cache where log records are built and stored before being posted to the log. Each PLC may hold multiple log records for a single transaction before they are flushed to the log (page chain) through the log semaphore. When a transaction commits or the memory fills with log records, the PLC associated with the transaction is flushed to the log. Because the log records for a complete transaction are immediately transferred through the log semaphore, contention on the log semaphore decreases. Contention alleviated by the PLC dramatically increases transaction throughput of the database server system.
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