Database altered.
SQL> ALTER DATABASE OPEN;或者shutdown immediate+startup Database altered.
检查数据库是否已经切换成功：
SQL> SELECT DATABASE_ROLE FROM V$DATABASE; DATABASE_ROLE ---------------- PRIMARY
至此，FAILOVER切换完成。这个时候应该马上对新的PRIMARY数据库进行备份。 数据库模式查看：
1. 首先查看当前的保护模式 ---primary数据库操作
SQL> select protection_mode,protection_level from v$database; PROTECTION_MODE PROTECTION_LEVEL -------------------- --------------------
MAXIMUM PERFORMANCE MAXIMUM PERFORMANCE 2. 设置新的数据保护模式并重启数据库 --primary数据库操作 当保护模式更改顺序：
maximize protection ---> maximize availability ----> maximize performance
当在把dataguard的保护级别按这上面的顺序减低的时候， 不需要primary库在mount状态，否则primary 必须在mount 状态。 如：
SQL> alter database set standby database to maximize availability; alter database set standby database to maximize availability *
ERROR at line 1:
ORA-01126: database must be mounted in this instance and not open in any instance
SQL> shutdown immediate Database closed. Database dismounted. ORACLE instance shut down. SQL> startup mount; ORACLE instance started.
Total System Global Area 167772160 bytes Fixed Size 1218316 bytes Variable Size 79694068 bytes Database Buffers 83886080 bytes Redo Buffers 2973696 bytes Database mounted.
SQL> alter database set standby database to maximize availability;
Database altered.
SQL> alter database open; alter database open *
ERROR at line 1:
ORA-03113: end-of-file on communication channel
报错了，这是因为最大可用性需要先修改日志传送方式为lgwr同步方式，否则，数据库是无法open.
Maximum protection/AVAILABILITY模式必须满足以下条件 Redo Archival Process: LGWR Network Tranmission mode: SYNC Disk Write Option: AFFIRM Standby Redo Logs: Yes
standby database type: Physical Only
SQL> alter system set log_archive_dest_2='service=orcl_st lgwr sync AFFIRM'; System altered.
SQL> shutdown immediate Database closed. Database dismounted. ORACLE instance shut down. SQL> startup mount; ORACLE instance started.
Total System Global Area 167772160 bytes Fixed Size 1218316 bytes Variable Size 79694068 bytes Database Buffers 83886080 bytes Redo Buffers 2973696 bytes Database mounted.
SQL> alter database set standby database to maximize availability; Database altered.
SQL> alter database open; Database altered.
SQL> select protection_mode,protection_level from v$database; PROTECTION_MODE PROTECTION_LEVEL -------------------- --------------------
MAXIMUM AVAILABILITY MAXIMUM AVAILABILITY
alter database set standby database to maximize performance;
提示：maximize后可跟{PROTECTION | AVAILABILITY | PERFORMANCE}，分别对应最大保护，最高可用性及最高性能。
在最大保护模式下，直接关闭备库是不行的，如果在备库上关闭数据库，会有如下提示： SQL> shutdown immediate
ORA-01154: database busy. Open, close, mount, and dismount not allowed now SQL>
在最大保护模式下，备库是不允许关闭的，此时首先关闭主库，然后备库就可以顺利关闭了。
注意： 主库的保护模式修改之后，备库的模式也会改变，和主库保持一致。