根据不同的保护模式（Protection Mode），主库Primary和备库Standby维持一种同步关系。这主要体现在一旦网络连接中断或者应用动作Apply中断，主库的事务形式上。那么，在默认保护模式情况下，如果主库不断的将新的redo log发送给Standby端，standby redo log写满或者切换满之后，Oracle的行为是什么样？下面通过实验来进行验证。
1、环境说明
笔者使用Oracle 11gR2进行测试，具体版本编号是11.2.0.4。当前Primary和Standby端已经搭建完成，Redo Apply动作正常。
主库Primary情况如下：
SQL> select open_mode, database_role from v$database;
OPEN_MODE? ? ? ? ? ? DATABASE_ROLE
-------------------- ----------------
READ WRITE? ? ? ? ? PRIMARY
SQL> select group#, sequence#, archived, status from v$log;
? ? GROUP#? SEQUENCE# ARCHIVED STATUS
---------- ---------- -------- ----------------
? ? ? ? 1? ? ? ? 37 NO? ? ? CURRENT
? ? ? ? 2? ? ? ? 35 YES? ? ? INACTIVE
? ? ? ? 3? ? ? ? 36 YES? ? ? INACTIVE
SQL> select recid, sequence#, ARCHIVED, APPLIED, DELETED from v$archived_log where name='vlifesb';
? ? RECID? SEQUENCE# ARCHIVED APPLIED? DELETED
---------- ---------- -------- --------- -------
（篇幅原因，有省略……）
? ? ? ? 20? ? ? ? 31 YES? ? ? YES? ? ? NO
? ? ? ? 22? ? ? ? 32 YES? ? ? YES? ? ? NO
? ? ? ? 24? ? ? ? 33 YES? ? ? YES? ? ? NO
? ? ? ? 26? ? ? ? 34 YES? ? ? YES? ? ? NO
? ? ? ? 28? ? ? ? 35 YES? ? ? YES? ? ? NO
? ? ? ? 30? ? ? ? 36 YES? ? ? NO? ? ? ? NO
15 rows selected
Standby端情况如下：
SQL> select open_mode, database_role from v$database;
OPEN_MODE? ? ? ? ? ? DATABASE_ROLE
-------------------- ----------------
READ ONLY WITH APPLY PHYSICAL STANDBY
SQL> select group#, dbid, sequence#, used, archived, status from v$standby_log;
? ? GROUP# DBID? ? ? ? ? ? ? ? ? SEQUENCE#? ? ? USED ARCHIVED STATUS
---------- -------------------- ---------- ---------- -------- ----------
? ? ? ? 4 4207470439? ? ? ? ? ? ? ? ? 37? ? 6491648 YES? ? ? ACTIVE
? ? ? ? 5 UNASSIGNED? ? ? ? ? ? ? ? ? ? 0? ? ? ? ? 0 NO? ? ? UNASSIGNED
? ? ? ? 6 UNASSIGNED? ? ? ? ? ? ? ? ? ? 0? ? ? ? ? 0 YES? ? ? UNASSIGNED
SQL> select recid, sequence#, ARCHIVED, APPLIED, DELETED from v$archived_log where name is not null;
? ? RECID? SEQUENCE# ARCHIVED APPLIED? DELETED
---------- ---------- -------- --------- -------
? ? ? ? 11? ? ? ? 32 YES? ? ? YES? ? ? NO
? ? ? ? 12? ? ? ? 33 YES? ? ? YES? ? ? NO
? ? ? ? 13? ? ? ? 34 YES? ? ? YES? ? ? NO
? ? ? ? 14? ? ? ? 35 YES? ? ? YES? ? ? NO
? ? ? ? 15? ? ? ? 36 YES? ? ? IN-MEMORY NO
当前两者同步开启状态，Standby Redo Log当前对应编号是37，与Primary端的Current Redo Log相匹配。
2、中断监听传输测试
“数据库宕机”是我们经常说到的数据库故障名词。但是宕机会有不同的故障点和故障方式。如果在Redo Apply的过程中，监听器发生故障终止服务，系统是什么方式和现象。
查看Standby端监听器情况，关闭监听器。
[oracle@vLIFE-URE-OT-DB-STANDBY ~]$ lsnrctl status
LSNRCTL for Linux: Version 11.2.0.4.0 - Production on 19-OCT-2015 11:07:58
Copyright (c) 1991, 2013, Oracle.? All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1521)))
STATUS of the LISTENER
------------------------
（篇幅原因，有省略……）
Service "vlifesb" has 2 instance(s).
? Instance "vlifesb", status UNKNOWN, has 1 handler(s) for this service...
? Instance "vlifesb", status READY, has 1 handler(s) for this service...
The command completed successfully
[oracle@vLIFE-URE-OT-DB-STANDBY ~]$ lsnrctl stop
LSNRCTL for Linux: Version 11.2.0.4.0 - Production on 19-OCT-2015 11:08:04
Copyright (c) 1991, 2013, Oracle.? All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1521)))
The command completed successfully
当终止Standby端监听程序的时候，主库立即在alert log中有对应反映。
******************************************
Fatal NI connect error 12541, connecting to:
?(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=172.16.19.90)(PORT=1521)))(CONNECT_DATA=(SERVICE_NAME=vlifesb)(CID=(PROGRAM=oracle)(HOST=vLIFE-URE-OT-DB-PRIMARY)(USER=oracle))))
? VERSION INFOR