Recovery with Checkpoint and Transaction Log Files

If a database becomes invalid or corrupted by a system or process failure, every connection to the database is invalidated. When an application reconnects to a failed database, the subdaemon allocates a new memory segment for the database and recovers its data from the checkpoint and transaction log files.

During recovery, the latest checkpoint file is read into memory. All transactions that have been committed since the last checkpoint and whose log records are on the file system are rolled forward from the appropriate transaction log files. Note that such transactions include all transactions that were committed durably as well as all transactions whose log records aged out of the in-memory log buffer. Uncommitted or rolled-back transactions are not recovered. See Checkpoint Operations, Transaction Logging and Error, Warning, and Informational Messages.