Database Server Activity That Is Physically Logged

All dbspace page modifications except the following ones are physically logged:

• Pages that do not have a valid database server address

  This situation usually occurs when the page was used by some other database server or a table that was dropped.

• Pages that the database server has not allocated and that are located in a dbspace where no table has been dropped since the last checkpoint.
• Pages for fuzzy operations such as inserts, deletes, and updates.

In case of multiple modifications before the next checkpoint, only one before-image is logged in the physical log (the first before-image).

Storing all before-images of page modifications in the physical log might seem excessive. But the database server stores the before-images in the physical log only until the next checkpoint. To control the amount of data that the database server logs, you can tune the checkpoint interval configuration parameter CKPTINTVL.

Physical Logging and Simple Large Objects

The database server pages in the physical log can be any database server page, including simple large objects in tblspaces. Even overhead pages (such as chunk free-list pages) are copied to the physical log before data on the page is modified and flushed to disk.