A database recovery log keeps a record of all changes made to a database, including the addition of new tables or updates to existing ones. This log is made up of a number of log extents, each contained in a separate file called a log file.
The database recovery log can be used to ensure that a failure (for example, a system power outage or application error) does not leave the database in an inconsistent state. In case of a failure, the changes already made but not committed are rolled back, and all committed transactions, which may not have been physically written to disk, are redone. These actions ensure the integrity of the database.
For more information, see Chapter 19, Recovering a Database.