L12 - Logging Protocols [CMU Database Systems Spring 2017]

15-721 Advanced Database Systems (Spring 2017)
Carnegie Mellon University

[CaetanoSauer]

To answer the question at 58:00: ARIES needs LSNs instead of txn IDs because of record-level locking. Two transactions may update the same two pages, but each in different order (e.g., t1->t2 in one page, t2->t1 in the other page). During redo recovery, the updates in each page must be applied in the order they actually happened, regardless of the final serializability order.

Whenever you're unsure of why ARIES does something weird, the answer is 99% of the time the combination of record-level locking with page-level recovery.

[よはべ]

At 1:14:07 (COMMAND LOGGING), would you give detailed explanation why physical logging has no problem with distributed transaction?