Hi, On Mon, Oct 16, 2023 at 08:46:48PM +0000, Murthy Nunna wrote: > It looks like the max value of autovacuum_freeze_max_age is 2 billion. > I am wondering why anybody wants to change this setting to a lower number? At a transaction age a bit above 2 billion, Postgres will stop accepting connections and one needs to vacuum manually, usually resulting in a long downtime. So one needs some (or rather a lot of) daylight between the time autovacuum decides to freeze a table and Postgres shutting down - it could be that autovacuum is held back by long-running transactions or unused replication slots or something. I would consider autovacuum_freeze_max_age up to 1 billion mostly safe (depending on the workload) and values up to 1.6 billion acceptable if good monitoring is in place and everybody knows what is going on. The other reason why want might not want to set autovacuum_freeze_max_age so high is that the pg_xact and pg_commit_ts sizes are proportional to autovacuum_freeze_max_age and take up more space if autovacuum_freeze_max_age is higher, which might be problematic if there is not a lot of storage present. Michael
