物理dataguard 正常切换脚色转换，switchover_status 状态改变

最新推荐文章于 2025-12-20 13:10:13 发布

转载最新推荐文章于 2025-12-20 13:10:13 发布 · 166 阅读

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#数据库

本文详细介绍了Oracle DataGuard环境中进行角色切换的过程，包括正常的主备切换流程、注意事项及故障转移(failover)的步骤。通过具体命令展示如何从主库切换到备用库，再从备用库切换回主库，以及在出现故障时如何快速完成切换。

正常切换

切换前：
主库：

SQL> select DATABASE_ROLE from v$database;

DATABASE_ROLE
----------------
PRIMARY

SQL> select OPEN_MODE,PROTECTION_MODE,PROTECTION_LEVEL,SWITCHOVER_STATUS from v$database;

OPEN_MODE PROTECTION_MODE PROTECTION_LEVEL SWITCHOVER_STATUS
---------- -------------------- -------------------- ------------------
READ WRITE MAXIMUM PERFORMANCE MAXIMUM PERFORMANCE TO STANDBY

SQL> SELECT COUNT(*) FROM V$SESSION WHERE USERNAME IS NOT NULL;

COUNT(*)
----------
1
在切换前，杀掉所有的数据库连接观察SWITCHOVER_STATUS，如果是 TO STANDBY，则可以直接切换
如果SESSIONS ACTIVE ，则用

备用库：

SQL> select DATABASE_ROLE from v$database;

DATABASE_ROLE
----------------
PHYSICAL STANDBY

SQL> select OPEN_MODE,PROTECTION_MODE,PROTECTION_LEVEL,SWITCHOVER_STATUS from v$database;

OPEN_MODE PROTECTION_MODE PROTECTION_LEVEL SWITCHOVER_STATUS
---------- -------------------- -------------------- ------------------
MOUNTED MAXIMUM PERFORMANCE MAXIMUM PERFORMANCE NOT ALLOWED

说明：

主库需要注意事项
A 如果switchover_status为TO_STANDBY说明可以转换
直接转换
alter database commit to switchover to physical standby;
B 如果switchover_status为SESSIONS ACTIVE 则关闭会话
SQL>alter database commit to switchover to physical standby with session shutdown;

在备库中操作，查看备库
SQL> select switchover_status from v$database;

A 如果switchover_status为TO_PRIMARY 说明标记恢复可以直接转换为primary库
SQL>alter database commit to switchover to primary

B 如果switchover_status为SESSION ACTIVE 就应该断开活动会话
SQL>alter database commit to switchover to primary with session shutdown;

C 如果switchover_status为NOT ALLOWED 说明切换标记还没收到，此时不能
执行转换。

切换中：

备用库
SQL> select DATABASE_ROLE from v$database;

DATABASE_ROLE
----------------
PHYSICAL STANDBY

SQL> select OPEN_MODE,PROTECTION_MODE,PROTECTION_LEVEL,SWITCHOVER_STATUS from v$database;

OPEN_MODE PROTECTION_MODE PROTECTION_LEVEL SWITCHOVER_STATUS
---------- -------------------- -------------------- ------------------
MOUNTED MAXIMUM PERFORMANCE MAXIMUM PERFORMANCE SESSIONS ACTIVE

切换后备用的状态，模式：

SQL> select DATABASE_ROLE from v$database;

DATABASE_ROLE
----------------
PRIMARY

SQL> select OPEN_MODE,PROTECTION_MODE,PROTECTION_LEVEL,SWITCHOVER_STATUS from v$database;

OPEN_MODE PROTECTION_MODE PROTECTION_LEVEL SWITCHOVER_STATUS
---------- -------------------- -------------------- ------------------
READ WRITE MAXIMUM PERFORMANCE MAXIMUM PERFORMANCE TO STANDBY

2. 检查环境：

确认主库和从库间网络连接通畅；

确认没有活动的会话连接在数据库中；

PRIMARY数据库处于打开的状态，STANDBY数据库处于MOUNT状态；

确保STANDBY数据库处于ARCHIVELOG模式；

如果设置了REDO应用的延迟，那么将这个设置去掉；

确保配置了主库和从库的初始化参数，使得切换完成后，DATA GUARD机制可以顺利的运行。

如果是最大保护模式，先变成最大性能模式：

3. 切换的顺序：先从主库到备用，再从备库到主库

主切备：

SQL> select DATABASE_ROLE from v$database;

DATABASE_ROLE
----------------
PRIMARY

SQL> select OPEN_MODE,PROTECTION_MODE,PROTECTION_LEVEL,SWITCHOVER_STATUS from v$database;

OPEN_MODE PROTECTION_MODE PROTECTION_LEVEL SWITCHOVER_STATUS
---------- -------------------- -------------------- ------------------
READ WRITE MAXIMUM PERFORMANCE MAXIMUM PERFORMANCE TO STANDBY

SQL>
SQL>
SQL> alter database commit to switchover to physical standby ;

Database altered.

SQL> shutdown immediate;
ORA-01507: database not mounted

ORACLE instance shut down.
SQL> startup nomount ;
ORACLE instance started.

Total System Global Area 3242987696 bytes
Fixed Size 733360 bytes
Variable Size 1174405120 bytes
Database Buffers 2063597568 bytes
Redo Buffers 4251648 bytes
SQL> alter database mount standby database;

Database altered.

SQL> alter database recover managed standby database disconnect from session;

Database altered.

SQL> select DATABASE_ROLE from v$database;

DATABASE_ROLE
----------------
PHYSICAL STANDBY

SQL> select OPEN_MODE,PROTECTION_MODE,PROTECTION_LEVEL,SWITCHOVER_STATUS from v$database;

OPEN_MODE PROTECTION_MODE PROTECTION_LEVEL SWITCHOVER_STATUS
---------- -------------------- -------------------- ------------------
MOUNTED MAXIMUM PERFORMANCE MAXIMUM PERFORMANCE TO PRIMARY

备切主
SQL> select DATABASE_ROLE from v$database;

DATABASE_ROLE
----------------
PHYSICAL STANDBY

SQL> select OPEN_MODE,PROTECTION_MODE,PROTECTION_LEVEL,SWITCHOVER_STATUS from v$database;

OPEN_MODE PROTECTION_MODE PROTECTION_LEVEL SWITCHOVER_STATUS
---------- -------------------- -------------------- ------------------
MOUNTED MAXIMUM PERFORMANCE MAXIMUM PERFORMANCE TO PRIMARY

SQL> alter database commit to switchover to primary;

Database altered.

SQL> SQL> SQL>
SQL>
SQL>
SQL> shutdown immediate;
ORA-01507: database not mounted

ORACLE instance shut down.
SQL> startup ;
ORACLE instance started.

Total System Global Area 3242987696 bytes
Fixed Size 733360 bytes
Variable Size 1174405120 bytes
Database Buffers 2063597568 bytes
Redo Buffers 4251648 bytes
Database mounted.
Database opened.

修改主备库的 tnsnames.ora
主库SESSIONS ACTIVE是正常primary状态下的结果。

DataGuard:Physical Standby Failover

接physical standby switchover

primary db :db2

standby db :db1

一般情况下failover都是表示primary数据库瘫痪，最起码也是起不来了，因此这种类型的切换基本上不需要primary数据库做什么操作。所以下列步骤中如果有提到primary和standby执行的，只是建议你如果primary还可以用，那就执行一下,即使不去执行，对failover来说也没有关系

1.检查归档文件是否连续，是否有gap

在standby库执行

SQL> select THREAD#,LOW_SEQUENCE#,HIGH_SEQUENCE# from v$archive_gap;

2.如果步骤1查询出来纪录，则在primary库上执行，否则跳过此步骤

在主库上执行语句，按步骤1查询出来的纪录找出归档文件

　SQL> SELECT NAME FROM V$ARCHIVED_LOG WHERE THREAD#=1 AND DEST_ID=1 AND SEQUENCE# BETWEEN XX AND XX;

　　--如果primary存在，拷贝相应的归档到STANDBY数据库，并注册.

　　SQL> ALTER DATABASE REGISTER PHYSICAL LOGFILE 'xxx';

3.检查归档文件是否完整

分别在primary/standby执行下列语句：

　　SQL> select distinct thread#,max(sequence#) over(partition by thread#) a from v$archived_log;

　　把相差的归档复制到待转换的standby服务器,并手工register