Implementing Commit(T)
Commit must be atomic. So it must be implemented by a disk write.
Suppose T wrote P, T committed, and then the system fails. P must be in stable storage.
Redo rule - Don’t commit a transaction until the after-images of all pages it wrote are on stable storage (in the database or log). (Ensures redo is possible.)
- Often called the Force-At-Commit rule