PersistOnCommit

PersistOnCommit is a configuration option used in transactional storage layers and event-sourcing systems to indicate when changes should be written to durable storage. It generally controls whether modifications made within a transaction are persisted to disk or other durable media as part of the commit phase.

When persistOnCommit is enabled, the system ensures that all changes encompassed by a transaction are persisted during the commit, making the effects durable once the commit completes. When it is disabled, changes may be buffered in memory or staged in a transaction log and persisted only after an explicit flush or at a later stage, trading durability for potential performance gains.

The concept is often implemented in conjunction with the storage engine’s durability guarantees, using mechanisms such as transactional writes, write-ahead logging, or log-based persistence. The exact semantics can vary by system: some implementations guarantee durability of all committed changes immediately, while others may allow deferred persistence with the expectation that a commit will ensure eventual durability.

Advantages of enabling persistOnCommit include stronger consistency and durability guarantees for committed transactions, as well as simpler reasoning about the visibility of changes. Trade-offs can include higher latency per commit and increased I/O pressure, particularly under high write throughput, since durability is tied to the commit boundary.

Typical use cases include relational and NoSQL databases, message and event stores, and frameworks that require atomic application of a batch of changes. Understanding the specific behavior of persistOnCommit within a given system is important for correctly balancing durability guarantees and performance. See also transactional durability, commit, and write-ahead logging.