Berkeley DB Reference Guide: Upgrading Berkeley DB Applications

Release 4.2: Client replication environments

In previous Berkeley DB releases, replication clients always behaved as if DB_TXN_NOSYNC behavior was configured, that is, clients would not write or synchronously flush their log when receiving a transaction commit or prepare message. However, applications needing a high level of transactional guarantee may need a write and synchronous flush on the client. By default in the Berkeley DB 4.2 release, client database environments write and synchronously flush their logs when receiving a transaction commit or prepare message. Applications not needing such a high level of transactional guarantee should use the environment's DB_TXN_NOSYNC flag to configure their client database environments to not do the write or flush on transaction commit, as this will increase their performance. Regardless of the setting of the DB_TXN_NOSYNC flag, clients will always write and flush on transaction prepare.

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