WriteAheadLog
Write-Ahead Logging (WAL) is a logging technique used in databases and other data-management systems to ensure atomicity and durability of transactions. The central idea is that all modifications to the database are recorded in a log before they are applied to the data files. By persisting the log first, the system can recover to a consistent state after a crash by replaying or undoing operations described in the log.
Mechanism: For each update, the system creates a log record describing the change and writes this record
Recovery: On startup after a crash, the system runs a recovery procedure that analyzes the log to
Adoption and variants: WAL is central to many modern relational databases, notably PostgreSQL, which uses a