--primary端查询v$archived_log视图，确认日志是否被应用：
set lines 300 pages 300
col name for a20
select name,dest_id,thread#,sequence#,standby_dest,applied,registrar,completion_time from v$archived_log
where standby_dest=‘YES‘
order by thread#,sequence#;
--primary端查询primary,standby的最大日志序列号是否一致：
select ‘Primary :‘ "DB Role",thread#,max(sequence#)
from v$archived_log
where standby_dest=‘NO‘
group by thread#
union
select ‘Standby :‘ "DB Role",thread#,max(sequence#)
from v$archived_log
where standby_dest=‘YES‘ and applied=‘YES‘
group by thread#
order by thread#;
DG观察日志传输
原文：https://www.cnblogs.com/liang545621/p/9407292.html
