Details of Physical Logging

This section describes the details of physical logging. It is provided to satisfy your curiosity; you do not need to understand the information here in order to manage your physical log.

The database server performs physical logging in the following six steps:

1. Reads the data page from disk to the shared-memory page buffer (if the data page is not there already)
2. Copies the unchanged page to the physical-log buffer
3. Reflects the change in the page buffer after an application modifies data
4. Flushes the physical-log buffer to the physical log on disk
5. Flushes the page buffer and writes it back to disk
6. When a checkpoint occurs, flushes the physical-log buffer to the physical log on disk and empties the physical log

The paragraphs that follow explain each step in detail.