Oracle学习之DATAGUARD(十一) snapshot database

Snapshot Standby，此功能可将备库置身于"可读写状态"用于不方便在生产环境主库中测试的内容，比如模拟上线测试等任务。当备库读写状态下任务完成后，可以非常轻松的完成Snapshot Standby数据库角色切换回备库角色，恢复与主库数据同步。在Snapshot Standby数据库状态下，备库是可以接受主库传过来的日志，但是不能够将变化应用在备库中。

物理备库要转换成Snapshot的前提条件

• 停止备库上的日志应用。

• 备库开启数据库闪回功能

下面演示，如果切换成snapshot。

1. 停止备库上的日志应用。

DGMGRL> edit database 11gdg2 set state=APPLY-OFF;Succeeded.DGMGRL>

2. 开启备库数据库闪回功能

SQL>  alter database flashback on;Database altered.

3.将备库转为snapshot

DGMGRL> CONVERT DATABASE 11GDG2 TO SNAPSHOT STANDBY;Converting database "11gdg2" to a Snapshot Standby database, please wait...Database "11gdg2" converted successfully

4. 此时，我们在主库上做些数据修改

SQL> select count(*) from t1;  COUNT(*)----------        56SQL> insert into t1 select * from t1;56 rows created.SQL> commit;Commit complete.

5. 在备库中修改数据

SQL> conn / as sysdbaConnected.SQL> select open_mode from v$database;OPEN_MODE------------------------------------------------------------READ WRITESQL> conn scott/tigerConnected.SQL> create table t2 as select * from t1;Table created.SQL> select count(*) from t2;  COUNT(*)----------        56SQL>

6. 将snapshot转为physical standby

DGMGRL> CONVERT DATABASE 11GDG2 TO PHYSICAL STANDBY;Converting database "11gdg2" to a Physical Standby database, please wait...Operation requires shutdown of instance "dgtst" on database "11gdg2"Shutting down instance "dgtst"...Database closed.Database dismounted.ORACLE instance shut down.Operation requires startup of instance "dgtst" on database "11gdg2"Starting instance "dgtst"...ORACLE instance started.Database mounted.Continuing to convert database "11gdg2" ...Operation requires shutdown of instance "dgtst" on database "11gdg2"Shutting down instance "dgtst"...ORA-01109: database not openDatabase dismounted.ORACLE instance shut down.Operation requires startup of instance "dgtst" on database "11gdg2"Starting instance "dgtst"...ORACLE instance started.Database mounted.Database "11gdg2" converted successfully

将备库打开

SQL> alter database open read only;Database altered.

7. 检查备库中t2表是否还存在

SQL> conn scott/tigerConnected.SQL> select * from t2;select * from t2              *ERROR at line 1:ORA-00942: table or view does not existSQL>

8.看看转换到snapshot后，对主库做的更改数据有没有被应用。

SQL> select count(*) from t1;  COUNT(*)----------       112SQL>

和第4步结论是一样的 。