An exploration of durability. Students will learn the physical layout of the WAL, how physiological logging works, and the mechanics of the checkpointer process. We will walk through the exact sequence of events during crash recovery and how PostgreSQL replays the WAL to guarantee the ACID property of Durability.

Outside Reading

• Official Docs: Chapter 30: Reliability and the Write-Ahead Log. (Mandatory reading on LSNs and asynchronous commits).
• Whitepaper: ARIES: A Transaction Recovery Method Supporting Fine-Granularity Locking and Partial Rollbacks (C. Mohan, 1992). Postgres recovery is heavily inspired by ARIES.
• GitHub Source: src/backend/access/transam/xlog.c. This is one of the most complex files in Postgres. Assign the reading of the block comments above StartupXLOG() to understand the crash recovery state machine.