- LRU cleaning, when you reach LRU_MAX_DIRTY
- A full checkpoint
- When the buffer is old and Informix is nearly at the point he would overwrite the logical log on disk that holds the transaction info. So it could be that a fuzzy checkpint flushes 'old' fuzzy operations.
Idea hbehind it is to do more LRU clenaing and less checkpint cleaning to reduce checkpoint time.