Fuzzy or Non-Blocking Checkpoints

Fuzzy checkpoints, or non-blocking checkpoints, enable transactions to run against the database while the checkpoint is in progress.

Fuzzy checkpoints do not obtain locks, and therefore have a minimal impact on other database activity. Because transactions may modify the database while a checkpoint operation is in progress, the resulting checkpoint file may contain both committed and uncommitted transactions. Furthermore, different portions of the checkpoint image may reflect different points in time. For example, one portion may have been written before a given transaction committed, while another portion was written afterward. The term "fuzzy checkpoint" derives its name from this fuzzy state of the database image.

To recover the database when the checkpoint files were generated from fuzzy checkpoint operations, TimesTen requires the most recent checkpoint file and the transaction log to bring the database into its most recent transaction-consistent state.