oracle ADG主备切换

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#oracle #数据库

本文详细描述了Oracle数据库从主库切换到备库，以及备库切换回为主库的过程，包括检查状态、执行SQL命令、解决错误（如媒体恢复需要）和调整日志应用等关键步骤。

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1.主库切换备库

SQL> select name,open_mode,switchover_status from v$database;

NAME OPEN_MODE SWITCHOVER_STATUS
--------- -------------------- --------------------
PROD1 READ WRITE TO STANDBY

SQL> alter system switch logfile;

System altered.

SQL> alter system archive log current;

System altered.

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

Database altered.

SQL> shutdown abort
ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.

Total System Global Area 849530880 bytes
Fixed Size 1348244 bytes
Variable Size 511708524 bytes
Database Buffers 331350016 bytes
Redo Buffers 5124096 bytes
Database mounted.
SQL> select switchover_status from v$database;

SWITCHOVER_STATUS
--------------------
RECOVERY NEEDED

SQL> alter database open;

Database altered.

SQL> select switchover_status from v$database;

SWITCHOVER_STATUS
--------------------
TO PRIMARY

2.备库切换主库

这里可能会出现错误：
ORA-16139: media recovery required。
下面有解决方法
解决完后，可以不要再次执行了。直接执行下面的命令。

SQL>  alter database commit to switchover to primary with session shutdown;                       
alter database commit to switchover to primary with session shutdown
*
ERROR at line 1:
ORA-16139: media recovery required

怀疑可能是由于有日志未应用造成的，执行如下语句查询：
SQL> select APPLIED,SEQUENCE# from v$archived_log;

APPLIED    SEQUENCE#
--------- ----------
YES                8
YES                9
YES               12
YES               13
YES               15
YES               16
YES               17
YES               10
YES               14
YES               11
YES               19

APPLIED    SEQUENCE#
--------- ----------
YES               18
NO                20
NO                21
NO                22
NO                23

16 rows selected.

正确步骤：

SQL> ALTER  DATABASE RECOVER MANAGED STANDBY  DATABASE DISCONNECT FROM SESSION;

Database altered.

SQL> alter database commit to switchover to primary;

Database altered.


SQL> alter database open;

Database altered.

SQL> select name,open_mode,switchover_status from v$database;

NAME OPEN_MODE SWITCHOVER_STATUS
--------- -------------------- --------------------
PROD1 READ WRITE TO STANDBY

3. 新备库（原主库）启用实时日志应用

SQL> alter database recover managed standby database using current logfile disconnect from session;
Database altered.
SQL> select name,open_mode,switchover_status from v$database;

NAME OPEN_MODE SWITCHOVER_STATUS
--------- -------------------- --------------------
RMANPRI READ ONLY RECOVERY NEEDED

4.新主库切换日志

SQL> alter system switch logfile;

System altered.

5、分别查看当前主备库切换后当前日志序列号

主库：

SQL> archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /oracle/archive
Oldest online log sequence 52
Next log sequence to archive 54
Current log sequence 54

备库：

SQL> archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /oracle/archive
Oldest online log sequence 53
Next log sequence to archive 0
Current log sequence 54

6、查看当前主备库状态

主库：

SQL> select name,open_mode,switchover_status from v$database;

NAME OPEN_MODE SWITCHOVER_STATUS
--------- -------------------- --------------------
RMANPRI READ WRITE TO STANDBY

 

备库：

SQL> select name,open_mode,switchover_status from v$database;

NAME OPEN_MODE SWITCHOVER_STATUS
--------- -------------------- --------------------
RMANPRI READ ONLY WITH APPLY NOT ALLOWED