The database file

When a database shuts down cleanly, 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 or complete.

The only time a database file is guaranteed to hold a complete and current copy of all data is immediately after a checkpoint completes. Following a checkpoint, all the contents of the database cache are on 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.

See also
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