PROTECTION_MODE is UNPROTECTED at standby database 分析

数据库版本

SQL> select * from v$version;

BANNER

--------------------------------------------------------------------------------------------------------------------------------

Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bi

PL/SQL Release 10.2.0.1.0 - Production

CORE     10.2.0.1.0       Production

TNS for Linux: Version 10.2.0.1.0 - Production

NLSRTL Version 10.2.0.1.0 – Production

1 、问题描述（data guard采用最大性能模式，但是备库的PROTECTION_MODE 竟是UNPROTECTED？）

主库

SQL> select DATABASE_ROLE,OPEN_MODE,PROTECTION_MODE from v$database;

DATABASE_ROLE                     OPEN_MODE             PROTECTION_MODE

-------------------------------- -------------------- ----------------------------------------

PRIMARY                           READ WRITE            MAXIMUM PERFORMANCE

备库

SQL> select DATABASE_ROLE,OPEN_MODE,PROTECTION_MODE from v$database;

DATABASE_ROLE                     OPEN_MODE             PROTECTION_MODE

-------------------------------- -------------------- ----------------------------------------

PHYSICAL STANDBY                  MOUNTED               UNPROTECTED

2 、问题补充描述

备库日志正常应用，主库做DML操作，备库read only开启也可以看到DML的结果。说明此data guard本身是没有问题的。但是为什么备库的PROTECTION_MODE 会出现 UNPROTECTED呢？万分不解，在朋友的帮助下找到了关于这个问题的描述如下：

maximize_standby_db_clause

Use this clause to specify the level of protection for the data in your database environment. You specify this clause from the primary database, which must be mounted but not open.

Note:

The PROTECTED and UNPROTECTED keywords have been replaced for clarity but are still supported. PROTECTED is equivalent to TO MAXIMIZE PROTECTION . UNPROTECTED is equivalent to TO MAXIMIZE PERFORMANCE .

官档链接： http://docs.oracle.com/cd/B19306_01/server.102/b14200/statements_1004.htm#SQLRF00802

3 、问题分析

根据官档的解释：

PROTECTED= TO MAXIMIZE PROTECTION

UNPROTECTED= TO MAXIMIZE PERFORMANCE

这样就不难看出了， 我们data guard中 PROTECTION_MODE =UNPROTECTED ，这根本就没有任何问题，只不过是想当于MAXIMIZE PERFORMANCE 的另一种叫法是 UNPROTECTED而已。

4 、总结：

PROTECTED= TO MAXIMIZE PROTECTION

UNPROTECTED= TO MAXIMIZE PERFORMANCE

一些关键性参数的理解问题。最好的解决办法就是找oracle官档。

终于也可以安心睡觉了，每天解决一点问题就是进步