六. 启用real-time apply，试验real-time query

1. 创建standby logfile。否则在执行“ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE DISCONNECT;”时，会报“ORA-38500: USING CURRENT LOGFILE option not available without stand”错误。

SQL> alter database add standby logfile group 11 '…/redo11.log' size 50M;

Database altered.

SQL> alter database add standby logfile group 12 '…/redo12.log' size 50M;

Database altered.

在duplicate结束后，备库没有添加standby redo log file。但是主库采用的是：lgwr async传送的日志。当备库的RFS进程接收到日志后，发现备库没有standby redo log的时候，备库会自动用ARCH将其写入归档文件。

在主库也添加一下standby redo log，以备切换。

2. 启用real-time apply，从而实现real-time query：

SQL> alter database recover managed standby database cancel;

SQL> ALTER DATABASE OPEN;

SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE DISCONNECT;

3. 测试real-time apply 和real-time query：

Primary：

SQL> create table rt(id number,name varchar2(20));

SQL> insert into rt values(1,'tianlesoftware');

SQL> commit;

SQL> alter system switch logfile;

Standby：

SQL> select open_mode from v$database;

OPEN_MODE

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

READ ONLY WITH APPLY

SQL> desc rt

 Name                Null?    Type

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

 ID                           NUMBER

 NAME                         VARCHAR2(30)

SQL> select * from rt;

        ID NAME

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

         1 tianlesoftware

注意：如果在主库执行 alter database clear unarchived logfile或alter database open resetlogs ,则dataguard要重建。