How to fix database isn't accepting commands to avoid wraparound data loss in PostgreSQL

SELECT pid, usename, state, backend_xmin, backend_xid,
       now() - xact_start AS duration, query
FROM pg_stat_activity
WHERE backend_xmin IS NOT NULL
ORDER BY age(backend_xmin) DESC;

-- For blocking transactions, try gentle termination first
SELECT pg_cancel_backend(pid) FROM pg_stat_activity
WHERE pid != pg_backend_pid()
  AND backend_xmin IS NOT NULL
  AND now() - xact_start > interval '1 hour';

-- If that doesn't work, force termination
SELECT pg_terminate_backend(pid) FROM pg_stat_activity
WHERE pid != pg_backend_pid()
  AND backend_xmin IS NOT NULL
  AND now() - xact_start > interval '1 hour';

SELECT datname, age(datfrozenxid) AS xid_age,
       2147483647 - age(datfrozenxid) AS txids_remaining,
       CASE
         WHEN 2147483647 - age(datfrozenxid) < 1000000 THEN 'CRITICAL'
         WHEN 2147483647 - age(datfrozenxid) < 10000000 THEN 'DANGER'
         ELSE 'MONITOR'
       END AS status
FROM pg_database
ORDER BY age(datfrozenxid) DESC;

SELECT c.oid::regclass AS table_name,
       greatest(age(c.relfrozenxid), age(t.relfrozenxid)) AS age
FROM pg_class c
LEFT JOIN pg_class t ON c.reltoastrelid = t.oid
WHERE c.relkind IN ('r', 'm')
ORDER BY age DESC
LIMIT 10;

-- Connect to each database and run this (as superuser)
VACUUM ANALYZE;

-- PostgreSQL 12+ with optimized freezing
VACUUM (INDEX_CLEANUP OFF, TRUNCATE OFF) large_table_name;

-- PostgreSQL 11 and earlier - just use plain VACUUM
VACUUM;

# Vacuum all databases with multiple workers
vacuumdb --all --jobs 4 --verbose

# Or target specific database
vacuumdb --dbname yourdb --jobs 4 --verbose

SELECT p.pid, p.datname, p.relid::regclass AS table_name,
       p.phase, p.heap_blks_total, p.heap_blks_scanned,
       round(100.0 * p.heap_blks_scanned / NULLIF(p.heap_blks_total, 0), 1) AS percent_complete,
       now() - a.xact_start AS duration
FROM pg_stat_progress_vacuum p
JOIN pg_stat_activity a ON p.pid = a.pid
ORDER BY p.pid;

SELECT pid, datname, duration, query
FROM (
  SELECT pid, datname, now() - xact_start AS duration, query
  FROM pg_stat_activity
  WHERE query LIKE '%VACUUM%'
) v
ORDER BY duration DESC;

-- Simple test insert
BEGIN;
  INSERT INTO test_write_check (value) VALUES ('test');
ROLLBACK;  -- Don't keep the test data

SELECT datname, age(datfrozenxid) AS xid_age,
       2147483647 - age(datfrozenxid) AS txids_remaining
FROM pg_database
WHERE datname = current_database();