Converting a Physical Standby Database into a Snapshot Standby Database

shutdown immedaite
startup mount
ALTER DATABASE CONVERT TO SNAPSHOT STANDBY;
alter database open;

Converting a Snapshot Standby Database into a Physical Standby Database

shutdown immedaite
startup mount
ALTER DATABASE CONVERT TO PHYSICAL STANDBY;
alter database open;--如果出现ORA-01507: database not mounted，重启数据库
alter database recover managed standby database disconnect from session;
alter database recover managed standby database using current logfile disconnect from session;