Checkpoints

2 articles

Database 15 Sep 2026 6 min read

PostgreSQL Full-Page Writes Raise WAL Volume After Checkpoints

A PostgreSQL page modified for the first time after a checkpoint can generate much more WAL than a later modification to the same page. With full_page_writes enabled, the first protected change records a full page image so crash recovery can reconstruct a page even if an operating-system failure interrupts a physical page write. That protection creates a recurring WAL pattern tied to checkpoint boundaries. A checkpoint resets the condition for pages, and subsequent writes gradually encounter pages that need a new full page image.

PostgreSQL Database

Database 15 Sep 2026 5 min read

PostgreSQL Full Page Writes Repair Torn Pages

A PostgreSQL data page can be larger than the atomic write unit provided by storage. If the host fails while a page is being written, part of that page may reach durable storage while another part remains from an older version. Recovery cannot safely apply ordinary change records to a page whose internal structure may already be inconsistent. full_page_writes addresses that failure mode. With the setting enabled, PostgreSQL records a complete image of a page in write-ahead log (WAL) on the first modification of that page after a checkpoint. During crash recovery, that image can replace a torn on-disk page before later WAL records are replayed.

PostgreSQL Database