Microsoft SQL Server 2014 Unleashed

The Checkpoint Process

During recovery, SQL Server examines the transaction log for each database and verifies whether the changes reflected in the log are also reflected in the database. In addition, it examines the log to determine whether any data changes that were written to the data were caused by a transaction that didn’t complete before the system failure.

As discussed earlier, a fully durable transaction COMMIT writes the log records for the transaction from the log buffer to the transaction log on disk (see Figure 28.1). Dirty data pages are written out either by the Lazy Writer or checkpoint process. The Lazy Writer process runs periodically to check whether the number of free buffers has fallen below a certain threshold, reclaims any ...