Oracle 11g中的snapshot standby特性

在Oracle 11g中,data guard最吸引人的,除了active data guard的实时查询特性（即可以以只读方式打开物理standby数据库的同时MRP进程能继续做recover）,快照备用数据库这个特性也是不错,比较适用于快速部署一个临时的与线上环境相同的测试数据库.它是通过还原点（restore point）和闪回数据库的原理（flashback database）,可以以读/写方式打开物理备用数据库,对数据库进行修改,之后再根据还原点,恢复到物理备用数据库。操作相当简单,以下测试:一.物理备用数据库到快照备用数据库
--查看当前备用数据库的角色
SQL> select open_mode,database_role from v$database;OPEN_MODE DATABASE_ROLE
-------------------- ----------------
READ ONLY WITH APPLY PHYSICAL STANDBY
--关闭并启动到mount
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.Total System Global Area 730714112 bytes
Fixed Size 2256832 bytes
Variable Size 482345024 bytes
Database Buffers 243269632 bytes
Redo Buffers 2842624 bytes
Database mounted.
--转换物理standby到快照standby
SQL> alter database convert to snapshot standby;Database altered.SQL> select status from v$instance;STATUS
------------
MOUNTEDSQL> alter database open;Database altered.
--查看当前备用数据库的角色
SQL> select open_mode,database_role from v$database;OPEN_MODE DATABASE_ROLE
-------------------- ----------------
READ WRITE SNAPSHOT STANDBY--可以看到,oracle 有建了一个还原点
SQL> select name,storage_size from v$restore_point;NAME
--------------------------------------------------------------------------------
STORAGE_SIZE
------------
SNAPSHOT_STANDBY_REQUIRED_08/10/2015 05:33:52
52428800

--测试是否可以修改数据库
SQL> create table scott.test02 as select * from dba_objects;Table created.SQL> select count（1） from scott.test02; COUNT（1）
----------
86267
二.快照备用数据库到物理备用数据库
--查看当前备用数据库的角色
SQL> select open_mode,database_role from v$database;OPEN_MODE DATABASE_ROLE
-------------------- ----------------
MOUNTED SNAPSHOT STANDBY--关闭并启动到mount
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.SQL> startup mount;
ORACLE instance started.Total System Global Area 730714112 bytes
Fixed Size 2256832 bytes
Variable Size 482345024 bytes
Database Buffers 243269632 bytes
Redo Buffers 2842624 bytes
Database mounted.--转换快照standby到物理standby
SQL> alter database convert to physical standby;Database altered.
SQL> shutdown immediate;
ORA-01507: database not mounted
ORACLE instance shut down.
SQL> startup
ORACLE instance started.Total System Global Area 730714112 bytes
Fixed Size 2256832 bytes
Variable Size 482345024 bytes
Database Buffers 243269632 bytes
Redo Buffers 2842624 bytes
Database mounted.
Database opened.
SQL> alter database recover managed standby database disconnect;Database altered.--查看当前备用数据库的角色
SQL> select open_mode,database_role from v$database;OPEN_MODE DATABASE_ROLE
-------------------- ----------------
READ ONLY WITH APPLY PHYSICAL STANDBY--查看在快照standby时建的测试表已经不存在了
SQL> select * from scott.test02;
select * from scott.test02
*
ERROR at line 1:
ORA-00942: table or view does not exist备注:
物理standby是最高保护模式（maximum protection）,是不能转换为snapshot standby的.
物理standby使用了standby redo log,在create restore point后,要alter system switch logfile;,以保证还原点的scn在物理standby库上是
归档的,不然可能无法成功闪回到还原点.
物理standby在切换为快照standby后,如果间隔很长时间,primary数据库产生的大量的重做日志,这样可以在转换为物理standby后,通过
对primary数据库的增量备份并recover到物理standby,来加快物理standby的还原速度.更多Oracle相关信息见Oracle 专题页面 http://www.linuxidc.com/topicnews.aspx？tid=12本文永久更新链接地址