Link together the WT_UPDATEs to represent the log. Also need something like hazard references so that active transactions can prevent pages they have modified from being reconciled. Eviction will scan through all cursors. If a cursor is looking at the page in question, there is a choice: for LRU, we've raced, just give up on that page.

The key points are that:

• transaction see their own updates, but not those of other uncommitted transactions; and
• either all or none of the changes from a transaction must be saved in a checkpoint.