Storage & Databases

Transaction log

Append-only record of every change for crash recovery.

In plain terms

Same idea as WAL. Postgres pg_wal, MySQL redo log, SQL Server transaction log. Replay on crash to recover committed transactions.

Origin

IBM System R (1976) and ARIES (Mohan et al., 1992) — the same provenance as WAL.

Where it shows up in production

PostgreSQL pg_wal The transaction log doubles as the replication stream.
MySQL InnoDB redo log Circular log file ahead of the data files for crash recovery.
SQL Server transaction log Backup-and-restore plus replication ride on this single log.

On Semicolony

Sources & further reading

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