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PostgreSQL · Concept

Write-ahead log

Write-Ahead Logging (WAL) records database changes before PostgreSQL writes the changed table and index pages. After a crash, PostgreSQL can replay the records to recover changes that were not yet written.

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Syntax

WAL records are created automatically by PostgreSQL; applications do not call a WAL command directly.

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  • Write-Ahead Logging (WAL)
  • Reliability
  • Asynchronous Commit
  • WAL Configuration
  • WAL Internals
  • wal_level

Source: PostgreSQL: Documentation: 18: 28.3. Write-Ahead Logging (WAL). Checked 2026-11-03.