immediate   Committed transactions are flushed to storage immediately upon a commit call before the commit operation completes.

grouped   Committed transactions are flushed to storage on a commit call, but only after a threshold you configure has been reached. You can configure either a transaction count threshold with the commit_flush_count database option or a time-based threshold with the commit_flush_timeout database option.

If set, both the commit_flush_count and the commit_flush_timeout options act as possible triggers for the commit flush; the first threshold that is met triggers the flush. When the flush occurs, UltraLite sets the counter and the timer back to 0. Then, both the counter and timer are monitored, until one of these thresholds is reached again.

on_checkpoint   Committed transactions are flushed to storage on a checkpoint operation. You can perform a checkpoint with any of the following:

• The CHECKPOINT statement. APIs that do not have a checkpoint method must use this SQL statement.
• The ULCheckpoint function for UltraLite embedded SQL.
• The Checkpoint method on a connection object in a C++ component.