5.3 Synchronization Requirements for Recoverability
In addition to guaranteeing serializability, synchronization is needed to implement abort easily.
When a transaction T aborts, the data manager wipes out all of T’s effects, including
- undoing T’s writes that were applied to the DB, and
- aborting transactions that read values written by T (these are called cascading aborts)
Example - w1[x] r2[x] w2[y]
- to abort T1, we must undo w1[x] and abort T2 (a cascading abort)