Parameter · Write-Ahead Log / Summarization
wal_summary_keep_time
Time for which WAL summary files should be kept. 0 disables automatic summary file deletion.
- Default:
10d - Type: integer (min)
- Range: 0 … 35791394min
- Applies: Reload
In plain words
The WAL summarizer deletes summary files older than this. Your incremental backups need summaries all the way back to the previous backup in the chain, so keep them longer than the gap between backups.
For DBAs and operators
Age is based on file modification time. Default 14400 min = 10 days; 0 disables automatic removal (it is then safe to delete files manually that no future incremental backup needs). Removal is done by the summarizer, so with summarize_wal = off nothing is removed at all.
Rule of thumb: longer than your full-backup interval plus slack. With weekly fulls and daily incrementals, 10 days is fine; with monthly fulls, raise it (or take incrementals relative to the previous incremental, which only needs the last day's summaries). Summary files are small (often KB to a few MB).
How to change it
Change in postgresql.conf or ALTER SYSTEM, then run SELECT pg_reload_conf().