Oracle通过视图和告警日志检查主库，物理和快照备库

通过以下语句获取主备库的当前角色，保护模式，保护级别，切换状态，快速启用，失效转换信息

select protection_mode,       protection_level,       database_role role,       switchover_status  from v$database;

获取fast-start 失效切换状态

select fs_failover_status           "fsfo status",       fs_failover_current_target   target,       fs_failover_threshold        threshold,       fs_failover_observer_present "observer present"  from v$database;

获取物理备库上的redo应用和传输状态

select process, status, thread#, sequence#, block#, blocks  from v$managed_standby;

查询归档日志文件的信息和历史归档信息

select thread#, sequence#, first_change#, next_change#   from v$archived_log;select thread#, sequence#, first_change#, next_change# from v$log_history;

查看被写入alert log中关于DG的事件信息

select message from v$dataguard_status

查看主库redo日志传输到目标端的状态，SCN表示最后一个在standby库上应用的redo日志的系统改变号。

select dest_id, applied_scn from v$archive_dest where target='standby';