10g datagurad的一次switchover
查询主库的状态：
SQL>select switchover_status from v$database;
SWITCHOVER_STATUS
--------------------
SESSIONSACTIVE
更换主库的角色：
SQL>alter database commit to switchover to physical standby with session shutdown;
Database altered.
这时alter_log有以下信息，说明自动建立了standby log：
standbyredo logfiles that match the primary database:
ALTERDATABASE ADD STANDBY LOGFILE 'srl1.f' SIZE 52428800;
ALTERDATABASE ADD STANDBY LOGFILE 'srl2.f' SIZE 52428800;
ALTERDATABASE ADD STANDBY LOGFILE 'srl3.f' SIZE 52428800;
ALTER DATABASE ADD STANDBY LOGFILE 'srl4.f' SIZE 52428800;
备库的switchover_status 的状态从not allowed改成了to primary:
SQL>select switchover_status from v$database;
SWITCHOVER_STATUS
--------------------
NOTALLOWED
SQL>select switchover_status from v$database;
SWITCHOVER_STATUS
--------------------
TOPRIMARY
将备库改成主库：
SQL>ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY WITH SESSION SHUTDOWN;
Database altered.
SQL>select switchover_status from v$database;
SWITCHOVER_STATUS
--------------------
TO STANDBY
SQL> select DATABASE_ROLE fromv$database;
DATABASE_ROLE
----------------
PRIMARY
测试一下，原来的主库已开始接收Log了。
SQL> alter system switchlogfile;
System altered.
新主库的alert_log:
RFS[4]: Identified database type as'physical standby'
Thu Aug 1 13:03:47 2013
Primary database is in MAXIMUMPERFORMANCE mode
RFS[2]: Successfully opened standbylog 5: '/u01/app/oracle/oradata/orcl/redo05.log'
再做一次switchover，恢复到最初的状态：
在主库执行：
SQL> select switchover_statusfrom v$database;
SWITCHOVER_STATUS
--------------------
SESSIONS ACTIVE
SQL> alter database commit to switchover tophysical standby with session shutdown;
Database altered.
在备库执行：
SQL> select switchover_statusfrom v$database;
SWITCHOVER_STATUS
--------------------
NOT ALLOWED
SQL> select switchover_status from v$database;
SWITCHOVER_STATUS
--------------------
TO PRIMARY
SQL> ALTER DATABASE COMMIT TOSWITCHOVER TO PRIMARY WITH SESSION SHUTDOWN;
Database altered.
SQL> select switchover_statusfrom v$database;
SWITCHOVER_STATUS
--------------------
TO STANDBY
分别重启主重库后：
SQL> startup mount
ORACLE instance started.
Total System Global Area 281018368 bytes
Fixed Size 1218944 bytes
Variable Size 100664960 bytes
Database Buffers 171966464 bytes
Redo Buffers 7168000 bytes
Database mounted.
SQL> select PROTECTION_MODE,PROTECTION_LEVEL from v$database;
PROTECTION_MODE PROTECTION_LEVEL
----------------------------------------
MAXIMUM AVAILABILITY MAXIMUM AVAILABILITY
SQL> recover managed standbydatabase disconnect from session;
Media recovery complete.
主库切换一次logfile;
SQL> alter system switch logfile;
System altered.
备库的日志：
Thu Aug 1 14:19:44 2013
Primary database is in MAXIMUMAVAILABILITY mode
Standby controlfile consistent withprimary
RFS[2]: Successfully opened standbylog 5: '/u01/app/oracle/oradata/orcl/redo05.log'
Thu Aug 1 14:19:48 2013
Media Recovery Log/u0