v$dataguard_stats里的transport lag与apply lag的含义

10.2.0.5 on windows 64 bit

官方文档的解释是

• APPLY LAG: Amount of time that the application of redo data on the standby database lags behind the primary database.

• TRANSPORT LAG: How much redo data (in time units) generated by the primary database is not available or applicable on the standby database at the time of computation.

实际环境：

primary db: 

select protection_mode,protection_level from v$database；

1 MAXIMUM AVAILABILITYMAXIMUM AVAILABILITY

physical standby db

select * from v$dataguard_stats

1 apply finish time+00 01:04:45.056 day(2) to second(3) interval28-MAY-2014 07:22:45
2 apply lag +00 12:20:27 day(2) to second(0) interval28-MAY-2014 07:22:45
3 estimated startup time24 second28-MAY-2014 07:22:45
4 standby has been openN 28-MAY-2014 07:22:45
5 transport lag+00 00:00:00 day(2) to second(0) interval28-MAY-2014 07:22:45

TRANSPORT LAG为0，但是APPLY LAG却不为0，不是很理解为啥。

另外可以通过如下方式看：

分别在primary database 和standby 上面查看当前current_scn

select currrent_scn from v$database; 然后将相应的scn转换成timestamp select scn_to_timestamp(1532667) from dual;