switchover步骤切换

主库
alter system switch logfile;

alter system set log_archive_dest_state_2='defer';

select switchover_status from v$database;

alter database commit to switchover to physical standby with session shutdown;

shutdown immediate;

startup mount;

alter database recover managed standby database disconnect;

备库
alter database recover managed standby database disconnect; 转换不需要cancel先停掉，防止报ORA-16139: media recovery required，可能是由于未应用日志引起，可先执行。

select switchover_status from v$database;

alter database commit to switchover to primary with session shutdown;

alter database open;

alter system set log_archive_dest_state_2='enable';