当前状态是dg1为主库，备库为dg2先检查主备库状态：dg1SQLselectname,database_role,OPEN_MODE,SWITCHOVER_STATUSfromv$database;DATABASE_ROLEOPEN_MODESWITCHO
当前状态是dg1为主库，备库为dg2
先检查主备库状态：
dg1
SQL> select name,database_role,OPEN_MODE,SWITCHOVER_STATUS from v$database;
DATABASE_ROLE OPEN_MODE SWITCHOVER_STATUS
---------------- ---------- --------------------
PRIMARY
READ WRITE SESSIONS ACTIVE
dg2
SQL> select database_role,OPEN_MODE,SWITCHOVER_STATUS from v$database;
DATABASE_ROLE OPEN_MODE SWITCHOVER_STATUS
---------------- ---------- --------------------
PHYSICAL STANDBY MOUNTED NOT ALLOWED
现在dg1（当前主库）上操作以下步骤：
SQL> alter database commit to switchover to physical standby with session shutdown;
Database altered.
SQL> shutdown immediate;
ORA-01507: database not mounted
ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.
Total System Global Area 390070272 bytes
Fixed Size
2021024 bytes
Variable Size
150997344 bytes
Database Buffers
234881024 bytes
Redo Buffers
2170880 bytes
Database mounted.
SQL> select switchover_status from v$database;
SWITCHOVER_STATUS
--------------------
TO PRIMARY
现在dg2（当前备库）上操作以下步骤：
SQL> select name,database_role,OPEN_MODE,SWITCHOVER_STATUS from v$database;
NAME
DATABASE_ROLE OPEN_MODE SWITCHOVER_STATUS
--------- ---------------- ---------- --------------------
ORCLDB PHYSICAL STANDBY MOUNTED TO PRIMARY
SQL> select switchover_status from v$database;
SWITCHOVER_STATUS
--------------------
TO PRIMARY
SQL> alter database commit to switchover to primary;
Database altered.
SQL> alter database open;
Database altered.
SQL> select name,database_role,OPEN_MODE,SWITCHOVER_STATUS from v$database;
NAME
DATABASE_ROLE OPEN_MODE SWITCHOVER_STATUS
--------- ---------------- ---------- --------------------
ORCLDB PRIMARY
READ WRITE SESSIONS ACTIVE
以上的操作已经完成了主备的切换，现在dg2为主库，dg1为备库，接下来我们在现在的主库dg2上做几次日志变化，，看dg1能否同步过来。
dg1上看已经归档的日志：
SQL> select registrar,creator thread#,sequence#,first_change#,next_change# from v$archived_log;
REGISTR THREAD# SEQUENCE# FIRST_CHANGE# NEXT_CHANGE#
------- ------- ---------- ------------- ------------
FGRD FGRD
29
586174
586196
dg2上经过几次日志切换，
SQL> select * from v$log;
GROUP# THREAD# SEQUENCE#
BYTES MEMBERS ARC STATUS
FIRST_CHANGE# FIRST_TIM
---------- ---------- ---------- ---------- ---------- --- ---------------- ------------- ---------
1
1
36 52428800
1 NO CURRENT
586469 05-JAN-14
2
1
34 52428800
1 YES INACTIVE
586464 05-JAN-14
3
1
35 52428800
1 YES INACTIVE
586467 05-JAN-14
可以看出现在日志已经到了36，那么我们在dg1上应用日志，应该会应用到日志35；
以下操作验证：
SQL> alter database recover managed standby database disconnect from session;
Database altered.
SQL> select registrar,creator thread#,sequence#,first_change#,next_change# from v$archived_log;
REGISTR THREAD# SEQUENCE# FIRST_CHANGE# NEXT_CHANGE#
------- ------- ---------- ------------- ------------
RFS
ARCH
34
586464
586467
RFS
ARCH
35
586467
586469
以上的主备切换过程就已经顺利进行完成。
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