Database Journaling

NuoDB’s architecture consists of interactive processes that operate over three layers: a management tier (brokers, a storage tier (Storage Managers) and a transaction tier (Transaction Engines).

The storage tier is responsible for maintaining a complete copy of the database. The atoms, or database elements, are persisted by the archive storage (for example disk). Atoms are written by a specific Storage Manager (SM) module called the archive. The journal is used to write all messages that update the state of an atom. These messages are subsequently applied to the database elements by the SM and persisted to the archive. Journaled messages are important because they are used to recover data lost by an SM that was unexpectedly terminated for any reason.

The following database options are available for the configuration of journaling:

  • --journal-dir

  • --journal-max-directory-entries

  • --journal-max-file-size-bytes

  • --journal-single-file

  • --journal-sync-method

For information on using these and other options, see Database Options.