列出副本 / 集群节点

Oracle

-- Standby destinations:
SELECT dest_id, destination, status, target
FROM v$archive_dest
WHERE status <> 'INACTIVE';
-- RAC instances: SELECT inst_id, instance_name, status FROM gv$instance;

Data Guard 配置也可通过 DGMGRL> SHOW CONFIGURATION 查看。

PostgreSQL

SELECT application_name, client_addr, state, sync_state
FROM pg_stat_replication;

仅在 PRIMARY 上列出已连接的副本；每行代表一个备库。

MySQL

SHOW REPLICAS;
-- Before 8.0.22: SHOW SLAVE HOSTS;

在源服务器上执行；显示设置了 report-host 的副本。SHOW SLAVE HOSTS 在 8.0.22–8.3 中是别名，并已在 8.4 中移除。

SQL Server

SELECT ar.replica_server_name, ars.role_desc,
       ars.connected_state_desc, ars.synchronization_health_desc
FROM sys.dm_hadr_availability_replica_states ars
JOIN sys.availability_replicas ar ON ars.replica_id = ar.replica_id;

role_desc 区分 PRIMARY/SECONDARY；synchronization_health_desc 给出整体健康状况。

MongoDB

rs.status().members.map(m => ({ name: m.name, state: m.stateStr, health: m.health }))

stateStr 返回 PRIMARY/SECONDARY/ARBITER；health 为 1 表示健康。

Redis

INFO replication
# If Sentinel is used:
# SENTINEL replicas <master-name>

slave0、slave1... 行给出每个副本的 ip/port/offset。