We have a large >20TB system just pg_upgraded from 9.5 to 9.6 as per the versions shown below. The system does <5M transactions/day based on sum(commit + abort) from pg_stat_database. Autovac is running all possible threads now and upon investigating I see that thousands of tables are now above the freeze threshold. Same tables all appear ~50M xids older than they did yesterday and the upgrade was less than 24 hours ago. I have a "safety" snap made of the system before upgrade that can be used for inspection. Any ideas why the age jump? select age(l.relfrozenxid), l.oid::regclass::text as relation, l.relkind, l.relpages, r.oid::regclass::text as "toast for" from pg_class l left join pg_class r on l.oid = r.reltoastrelid where l.relkind in ('r', 't') order by age desc, relation limit :limit ii postgresql-9.5 9.5.12-1.pgdg16.04+1 amd64 object-relational SQL database, version 9.5 server ii postgresql-9.6 9.6.8-1.pgdg16.04+1 amd64 object-relational SQL database, version 9.6 server Thanks -- Jerry Sievers Postgres DBA/Development Consulting e: postgres.consulting@xxxxxxxxxxx p: 312.241.7800