顺便讨论一下，那么什么时候会找不到合适的standby redo log用呢？笔者遇到过文件不存在，另外如果出现standby端arch进程来不及将日志写入归档，应该也会写入到另一组的standby redo log中。
下面如果启动程序，进行更新。
SQL> alter database recover managed standby database using current logfile disconnect from session;
Database altered
在日志中看到应用日志过程：
Mon Oct 19 11:23:53 2015
alter database recover managed standby database using current logfile disconnect from session
Attempt to start background Managed Standby Recovery process (vlifesb)
Mon Oct 19 11:23:53 2015
MRP0 started with pid=28, OS id=15602
MRP0: Background Managed Standby Recovery process started (vlifesb)
started logmerger process
Mon Oct 19 11:23:58 2015
Managed Standby Recovery starting Real Time Apply
Parallel Media Recovery started with 4 slaves
Waiting for all non-current ORLs to be archived...
All non-current ORLs have been archived.
Media Recovery Log /u01/app/oracle/fast_recovery_area/VLIFESB/archivelog/2015_10_19/o1_mf_1_39_c28rgoqb_.arc
Media Recovery Log /u01/app/oracle/fast_recovery_area/VLIFESB/archivelog/2015_10_19/o1_mf_1_40_c28rgpq1_.arc
Media Recovery Log /u01/app/oracle/fast_recovery_area/VLIFESB/archivelog/2015_10_19/o1_mf_1_41_c28rgtl2_.arc
Media Recovery Waiting for thread 1 sequence 42 (in transit)
Recovery of Online Redo Log: Thread 1 Group 4 Seq 42 Reading mem 0
Mem# 0: /u01/app/oracle/oradata/VLIFESB/onlinelog/o1_mf_4_c265gc9q_.log
Mem# 1: /u01/app/oracle/fast_recovery_area/VLIFESB/onlinelog/o1_mf_4_c265gcfk_.log
Completed: alter database recover managed standby database using current logfile disconnect from session
这个过程中，进行standby recovery操作，先从归档日志中找到没有apply的进行应用。之后应用standby redo log。
此时，apply成功，能够追上Primary。
SQL> select group#, dbid, sequence#, used, archived, status from v$standby_log;
GROUP# DBID SEQUENCE# USED ARCHIVED STATUS
---------- -------------------- ---------- ---------- -------- ----------
4 4207470439 42 107520 YES ACTIVE
5 UNASSIGNED 0 0 NO UNASSIGNED
6 UNASSIGNED 0 0 YES UNASSIGNED
SQL> select recid, sequence#, ARCHIVED, APPLIED, DELETED from v$archived_log;
RECID SEQUENCE# ARCHIVED APPLIED DELETED
---------- ---------- -------- --------- -------
（篇幅原因，有省略……）
15 36 YES YES NO
16 37 YES YES NO
17 38 YES YES NO
18 39 YES YES NO
19 40 YES YES NO
20 41 YES IN-MEMORY NO
20 rows selected
4、结论