snapshot standby database

快照备库接收和归档主库发送来的redo，但是不会应用；切换成physical standby之后会自动开启redo apply。
快照standby不可以参加主备切换；在最大保护性模式下，如果只有一个备库，则不可以将备库转成snapshot standby。

将Physical Standby Database转换成Snapshot Standby Database

1.停止redo apply

SQL> alter database recover managed standby database cancel;

2.确保数据是mounted状态，而不是open状态

SQL> select open_mode,database_role from v$database;

OPEN_MODE            DATABASE_ROLE
-------------------- ----------------
MOUNTED              PHYSICAL STANDBY

SQL>

3.确认已经创建好fast recovery area(不需要对数据库开启闪回)

SQL> show parameter db_recovery_file

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_recovery_file_dest                string      /s01/app/oracle/flash
db_recovery_file_dest_size           big integer 4G
SQL>

4.执行转换

SQL> alter database convert to snapshot standby ;

Database altered.

SQL> select open_mode,database_role from v$database;

OPEN_MODE            DATABASE_ROLE
-------------------- ----------------
MOUNTED              SNAPSHOT STANDBY

SQL>

5.将数据打开

SQL> alter database open;

Database altered.

#打开模式已经改变，但是角色不变
SQL> select open_mode,database_role from v$database;

OPEN_MODE            DATABASE_ROLE
-------------------- ----------------
READ WRITE           SNAPSHOT STANDBY

SQL>

将Snapshot Standby Database切换成Physical Standby Database

1.如果是RAC环境，要先关掉所有实例
2.将数据库启动到mount状态
3.执行切换

SQL> select open_mode,database_role from v$database;

OPEN_MODE            DATABASE_ROLE
-------------------- ----------------
MOUNTED              SNAPSHOT STANDBY

SQL> alter database convert to physical standby;

Database altered.

#转换命令结束后，数据库会自动被dismounted，需要关闭重启数据库。
SQL> select open_mode,database_role from v$database;
select open_mode,database_role from v$database
                                    *
ERROR at line 1:
ORA-01507: database not mounted

SQL> startup mount
ORA-01081: cannot start already-running ORACLE - shut it down first
SQL> shutdown immediate
ORA-01507: database not mounted

ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.

Total System Global Area  430075904 bytes
Fixed Size                  2253944 bytes
Variable Size             184552328 bytes
Database Buffers          239075328 bytes
Redo Buffers                4194304 bytes
Database mounted.
SQL>