DG 开启/关闭snapshot

背景：

灾备库每周有发版需求，需要开启snapshot 读写模式验证版本功能。

1.开启 dg snapshot

#取消实时同步
alter database recover managed standby database cancel;

#查看数据库状态
select database_role,open_mode from v$database;

#切换到 snapshot standby 模式(是在open状态下操作的)
alter database convert to snapshot standby;

#再次查看状态：(变为 mount)
select database_role,open_mode from v$database;
select flashback_on from v$database;

#最后启动数据库到open状态下(已经变为 read write,可以做任何测试操作)
alter database open;

select database_role,open_mode from v$database;

2.关闭 dg snapshot

#恢复物理备库,数据库需要在 mount 下完成切换：
select database_role,open_mode from v$database;
shutdown immediate;
startup mount;
alter database convert to physical standby;


#切换完成后,数据库需要再次重启至 mount
shutdown immediate;
startup mount;


#备库开启同步
alter database recover managed standby database using current logfile disconnect from session;
select database_role,open_mode from v$database;


alter database recover managed standby database cancel;
alter database open;
select database_role,open_mode from v$database;


#备库开启同步：
alter database recover managed standby database using current logfile disconnect from session;