ReplicatedMergeTree operations, failover procedures, lag diagnosis, quorum writes, and Keeper management.
Load when users ask about replication setup, lag, failover, or Keeper/ZooKeeper.
ReplicatedMergeTree('/clickhouse/tables/{shard}/{database}/{table}', '{replica}')system.replicas — per-table status: absolute_delay, queue_size, is_leader, is_readonlysystem.replication_queue — pending operations: fetches, merges, mutationsabsolute_delay = 0 — fully caught upis_readonly = 0 — accepting writesqueue_size < 10 — healthy queueactive_replicas = total_replicas — all replicas onlineSELECT * FROM system.replicas WHERE is_readonly = 1SELECT * FROM system.zookeeper WHERE path = '/'SYSTEM DROP REPLICA 'replica_name' FROM TABLE db.tableSET insert_quorum = 2 — wait for N replicas to confirmSET insert_quorum_parallel = 1 — parallel quorum inserts (v21.8+)SET insert_quorum_timeout = 60000 — timeout in mssystem.zookeeper table for browsing ZK tree/clickhouse/tables/ for table metadataSELECT * FROM system.asynchronous_metrics WHERE metric LIKE '%Keeper%'SYSTEM SYNC REPLICA db.table to force sync