Answer
WAL logs every change before writing to data files. WAL archiving stores old WAL segments enabling point-in-time recovery.
Quick Answer
WAL records every change before applying it - on crash, replay WAL from last checkpoint to recover. WAL archiving copies WAL segments to a safe location (S3, network) using archive_command. For DR: take a base backup (pg_basebackup), then archive WAL continuously. PITR: restore from base backup + replay archived WAL to any moment in time. Essential for zero data loss recovery and creating standbys from backups.
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SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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Source: SugharaIQ