ASA Database Administration Guide
Backup and Data Recovery
Understanding backups
When a database is shut down, the database file holds a complete and current copy of all the data in the database. When a database is running, however, the database file is generally not current.
The only time a database file is guaranteed to hold a complete and current copy of all data is when a checkpoint takes place. At a checkpoint, all the contents of the database cache are written out to the disk.
The database server checkpoints a database under the following conditions:
As part of the database shutdown operations
When the amount of time since the last checkpoint exceeds the database option CHECKPOINT_TIME
When the estimated time to do a recovery operation exceeds the database option RECOVERY_TIME
When the database server is idle long enough to write all dirty pages
When a connection issues a CHECKPOINT statement
When the database server is running without a transaction log and a transaction is committed
Between checkpoints, you need both the database file and another file, called the transaction log, to ensure that you have a complete copy of all committed transactions.
For more information about checkpoints, see Checkpoints and the checkpoint log, and How the database server decides when to checkpoint.