What is Write-Ahead Logging (WAL) in PostgreSQL?

WAL ensures data integrity by logging changes before applying them to data files.

How WAL Works:
• Changes written to WAL first
• Then applied to data files
• Ensures crash recovery
• Enables point-in-time recovery

WAL Configuration:

-- Key parameters
wal_level = replica
max_wal_size = 1GB
checkpoint_completion_target = 0.9
archive_mode = on
archive_command = 'cp %p /archive/%f'

Benefits:
• Data durability
• Crash recovery
• Replication support
• Backup consistency