The server returns to the last-checkpoint state

To return all disk pages to their condition at the time of the most recent checkpoint, the database server writes the before-images stored in the physical log to shared memory and then back to disk. Each before-image in the physical log contains the address of a page that was updated after the checkpoint. When the database server writes each before-image page in the physical log to shared memory and then back to disk, changes to the database server data since the time of the most recent checkpoint are undone. The database server is now physically consistent. The following figure illustrates this step.
Figure 1. Writing all remaining before-images in the physical log back to disk
The paragraphs that precede this figure describe the content of the figure.

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