Oracle一对多(一主多备)的DG环境如何进行switchover切换？

本文主要分享Oracle一对多(一主多备)的DG环境的switchover切换，如何进行主从切换，切换后怎么恢复正常同步？

1、环境说明

本文的环境为一主两备，数据库版本为11.2.0.4，主要信息如下：

数据库IP	db_unique_name	原角色（切换前）	目标角色（切换后）
10.10.10.160	ora11g	主库	备库
10.10.10.41	dgora11g	备库	主库
10.10.10.47	sbora11g	备库	备库

说明：
（1）当前主库为10.10.10.160，10.10.10.41 和10.10.10.47是它的两个备库。

​（2）switchover切换后，10.10.10.41变为主库，10.10.10.160和10.10.10.47成为它的两个备库。

2、主要参数配置

以下是相关数据库的主要参数配置信息（以db_unique_name进行区分）：

ora11g:

set linesize 500 pages 0
col value for a100
col name for a50
select name, value
from v$parameter
where name in ('db_name','db_unique_name',
'log_archive_config',
'log_archive_dest_1','log_archive_dest_2',
'log_archive_dest_state_1',
'log_archive_dest_state_2',
'remote_login_passwordfile',
'log_archive_format',
'log_archive_max_processes',
'fal_server','db_file_name_convert',
'log_file_name_convert',
'standby_file_management')
/db_file_name_convert				   /u01/oradata/dgora11g, /u01/oradata/ora11g, /u01/oradata/sbora11g, /u01/oradata/ora11g
log_file_name_convert				   /u01/oradata/dgora11g, /u01/oradata/ora11g, /u01/oradata/sbora11g, /u01/oradata/ora11g
log_archive_dest_1				   location=/u01/oradata/archivelog VALID_FOR=(ALL_LOGFILES,ALL_ROLES) db_unique_name=ora11g
log_archive_dest_2				   SERVICE=dgora11g LGWR ASYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) db_unique_name=dgora11g
log_archive_dest_state_1			   ENABLE
log_archive_dest_state_2			   ENABLE
fal_server					   dgora11g, sbora11g
log_archive_config				   DG_CONFIG=(ora11g,dgora11g,sbora11g)
log_archive_format				   %t_%s_%r.dbf
log_archive_max_processes			   4
standby_file_management 			   AUTO
remote_login_passwordfile			   EXCLUSIVE
db_name 					   ora11g
db_unique_name					   ora11g

dgora11g:

db_file_name_convert				   /u01/oradata/ora11g, /u01/oradata/dgora11g
log_file_name_convert				   /u01/oradata/ora11g, /u01/oradata/dgora11g
log_archive_dest_1				   location=/u01/oradata/archivelog VALID_FOR=(ALL_LOGFILES,ALL_ROLES) db_unique_name=dgora11g
log_archive_dest_2				   SERVICE=ora11g LGWR ASYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) db_unique_name=ora11g
log_archive_dest_state_1			   ENABLE
log_archive_dest_state_2			   ENABLE
fal_server					   ora11g
log_archive_config				   DG_CONFIG=(ora11g,dgora11g)
log_archive_format				   %t_%s_%r.dbf
log_archive_max_processes			   4
standby_file_management 			   AUTO
remote_login_passwordfile			   EXCLUSIVE
db_name 					   ora11g
db_unique_name					   dgora11g

sbora11g:

db_file_name_convert				   /u01/oradata/ora11g, /u01/oradata/sbora11g
log_file_name_convert				   /u01/oradata/ora11g, /u01/oradata/sbora11g
log_archive_dest_1				   location=/u01/oradata/archivelog VALID_FOR=(ALL_LOGFILES,ALL_ROLES) db_unique_name=sbora11g
log_archive_dest_2				   SERVICE=ora11g LGWR ASYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) db_unique_name=ora11g
log_archive_dest_state_1			   ENABLE
log_archive_dest_state_2			   ENABLE
fal_server					   ora11g
log_archive_config				   DG_CONFIG=(ora11g,sbora11g)
log_archive_format				   %t_%s_%r.dbf
log_archive_max_processes			   4
standby_file_management 			   AUTO
remote_login_passwordfile			   EXCLUSIVE
db_name 					   ora11g
db_unique_name					   sbora11g

3、切换前检查

切换前，确认备库同步情况，有没有延迟

dgora11g:

sys@dgora11g> select value from v$dataguard_stats where name='transport lag';VALUE
----------------------------------------------------------------
+00 00:00:00sys@dgora11g> select value from v$dataguard_stats where name='apply lag'; VALUE
----------------------------------------------------------------
+00 00:00:00--检查最新归档到的日志号及是否有gapsys@dgora11g> SELECT UNIQUE THREAD# AS THREAD, MAX(SEQUENCE#) OVER (PARTITION BY thread#) AS LAST from V$ARCHIVED_LOG;THREAD	 LAST
---------- ----------1	  289sys@dgora11g> SELECT THREAD#, LOW_SEQUENCE#, HIGH_SEQUENCE# FROM V$ARCHIVE_GAP;no rows selected

sbora11g:

sys@sbora11g > select value from v$dataguard_stats where name='transport lag';VALUE
----------------------------------------------------------------
+00 00:00:00sys@sbora11g > select value from v$dataguard_stats where name='apply lag';VALUE
----------------------------------------------------------------
+00 00:00:00
sys@sbora11g > SELECT UNIQUE THREAD# AS THREAD, MAX(SEQUENCE#) OVER (PARTITION BY thread#) AS LAST from V$ARCHIVED_LOG;THREAD	 LAST
---------- ----------1	  289sys@sbora11g > SELECT THREAD#, LOW_SEQUENCE#, HIGH_SEQUENCE# FROM V$ARCHIVE_GAP;no rows selected

检查确认两个备库实时同步，没有延时后，才能切换。

4、switchover切换

在切换时，在主库上是不可以选择我要切换到哪个备库的，这个选择是在备库上选择的，下面进行SWITCHOVER切换。

–主库状态

sys@ora11g> col name for a10;
sys@ora11g> set linesize 100;
sys@ora11g> select name,open_mode, database_role, switchover_status, force_logging, dataguard_broker, guard_status from v$database;NAME	   OPEN_MODE		DATABASE_ROLE	 SWITCHOVER_STATUS    FOR DATAGUAR GUARD_S
---------- -------------------- ---------------- -------------------- --- -------- -------
ORA11G	   READ WRITE		PRIMARY 	 TO STANDBY	      YES DISABLED NONE

–备库状态

dgora11g:

sys@dgora11g> col name for a10;
sys@dgora11g> set linesize 100;
sys@dgora11g> select name,open_mode, database_role, switchover_status, force_logging, dataguard_broker, guard_status from v$database;NAME	   OPEN_MODE		DATABASE_ROLE	 SWITCHOVER_STATUS    FOR DATAGUAR GUARD_S
---------- -------------------- ---------------- -------------------- --- -------- -------
ORA11G	   MOUNTED		PHYSICAL STANDBY NOT ALLOWED	      YES DISABLED NONE

sbora11g:

sys@sbora11g > col name for a10;
sys@sbora11g > set linesize 100;
sys@sbora11g > select name,open_mode, database_role, switchover_status, force_logging, dataguard_broker, guard_status from v$database;NAME	   OPEN_MODE		DATABASE_ROLE	 SWITCHOVER_STATUS    FOR DATAGUAR GUARD_S
---------- -------------------- ---------------- -------------------- --- -------- -------
ORA11G	   MOUNTED		PHYSICAL STANDBY NOT ALLOWED	      YES DISABLED NONE

–将主库转为物理备库

ora11g:

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

切换后，这个数据库已经备关闭，启动数据库，这个数据库已经变为备库，启动MRP进程。

sys@ora11g> startup;
ORACLE instance started.Total System Global Area 3691200512 bytes
Fixed Size		    2258680 bytes
Variable Size		 1392511240 bytes
Database Buffers	 2281701376 bytes
Redo Buffers		   14729216 bytes
Database mounted.
Database opened.
sys@ora11g> alter database recover managed standby database using current logfile disconnect from session;Database altered.或 alter database recover managed standby database using current logfile disconnect from session parallel 4; --检查状态，可以看到已变为从库
sys@ora11g> select name,open_mode, database_role, switchover_status, force_logging, dataguard_broker, guard_status from v$database;NAME	   OPEN_MODE		DATABASE_ROLE	 SWITCHOVER_STATUS    FOR DATAGUAR GUARD_S
---------- -------------------- ---------------- -------------------- --- -------- -------
ORA11G	   READ ONLY WITH APPLY PHYSICAL STANDBY TO PRIMARY	      YES DISABLED NONE

PS：主库切换后，两个备库均变为TO PRIMARY状态，这时就要选择切换哪个备库为主库了。

dgora11g:

sys@dgora11g> col name for a10;
sys@dgora11g> set linesize 100;
sys@dgora11g> select name,open_mode, database_role, switchover_status, force_logging, dataguard_broker, guard_status from v$database;NAME	   OPEN_MODE		DATABASE_ROLE	 SWITCHOVER_STATUS    FOR DATAGUAR GUARD_S
---------- -------------------- ---------------- -------------------- --- -------- -------
ORA11G	   MOUNTED		PHYSICAL STANDBY TO PRIMARY	      YES DISABLED NONE

sbora11g:

sys@sbora11g > col name for a10;
sys@sbora11g > set linesize 100;
sys@sbora11g > select name,open_mode, database_role, switchover_status, force_logging, dataguard_broker, guard_status from v$database;NAME	   OPEN_MODE		DATABASE_ROLE	 SWITCHOVER_STATUS    FOR DATAGUAR GUARD_S
---------- -------------------- ---------------- -------------------- --- -------- -------
ORA11G	   MOUNTED		PHYSICAL STANDBY TO PRIMARY	      YES DISABLED NONE

–备库切换成主库

这里选择sbora11g这个备库切换为主库：

sys@sbora11g > alter database commit to switchover to primary with session shutdown;Database altered.sys@sbora11g > alter database open;Database altered.sys@sbora11g > select name,open_mode, database_role, switchover_status, force_logging, dataguard_broker, guard_status from v$database;NAME	   OPEN_MODE		DATABASE_ROLE	 SWITCHOVER_STATUS    FOR DATAGUAR GUARD_S
---------- -------------------- ---------------- -------------------- --- -------- -------
ORA11G	   READ WRITE		PRIMARY 	 TO STANDBY	      YES DISABLED NONE

5、新主库参数调整

log_archive_config、log_archive_dest_3还需加上从库dgora11g

sys@sbora11g > show parameter archive;NAME				     TYPE	 VALUE
------------------------------------ ----------- ------------------------------
archive_lag_target		     integer	 0
log_archive_config		     string	 DG_CONFIG=(ora11g,sbora11g)
log_archive_dest		     string
log_archive_dest_1		     string	 location=/u01/oradata/archivelog VALID_FOR=(ALL_LOGFILES,ALL_ROLES) db_unique_name=sbora11g
log_archive_dest_10		     string
log_archive_dest_11		     string
log_archive_dest_12		     string
log_archive_dest_13		     string
log_archive_dest_14		     string
log_archive_dest_15		     string
log_archive_dest_16		     string
log_archive_dest_17		     string
log_archive_dest_18		     string
log_archive_dest_19		     string
log_archive_dest_2		     string	 SERVICE=ora11g LGWR ASYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) db_unique_name=ora11g
............................................
log_archive_dest_3		     string--log_archive_config 需将三节点都加上
alter system set log_archive_config='DG_CONFIG=(sbora11g,ora11g,dgora11g)' scope=both sid='*';
alter system set log_archive_dest_3='SERVICE=dgora11g LGWR ASYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) db_unique_name=dgora11g' scope=both sid='*';
alter system set fal_server='ora11g','dgora11g' scope=both sid='*';
alter system set log_archive_dest_state_3=defer scope=both sid='*';
alter system set log_archive_dest_state_3=enable scope=both sid='*';

6、备库参数调整

–log_archive_config 若未设置，需将三节点都加上

--log_archive_config需将三节点都加上
--dgora11g 修改目标主库为sbora11g
sys@dgora11g> show parameter config;NAME				     TYPE	 VALUE
------------------------------------ ----------- ------------------------------
dg_broker_config_file1		     string	 /u01/app/oracle/product/11.2.0/db/dbs/dr1dgora11g.dat
dg_broker_config_file2		     string	 /u01/app/oracle/product/11.2.0/db/dbs/dr2dgora11g.dat
log_archive_config		     string	 DG_CONFIG=(ora11g,dgora11g)
sys@dgora11g> alter system set log_archive_config='DG_CONFIG=(sbora11g,ora11g,dgora11g)' scope=both sid='*';System altered.--因为dgora11g这个数据库之前的主是ora11g(现在已经变成了备库)，需要把dgora11g的主改成sbora11g。alter system set log_archive_dest_2='SERVICE=sbora11g LGWR ASYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) db_unique_name=sbora11g' scope=both sid='*';alter system set FAL_SERVER='ora11g','sbora11g';若新的主库不在备库的DG_CONFIG配置里，主库会报错：
ARC3: Archivelog destination LOG_ARCHIVE_DEST_3 disabled: destination Data Guard configuration error
Archived Log entry 29 added for thread 1 sequence 300 ID 0x108ef4ac dest 1:
Fri Aug 09 20:16:12 2024
LNS: Standby redo logfile selected for thread 1 sequence 301 for destination LOG_ARCHIVE_DEST_2--ora11g备库已经配置，不用修改
sys@ora11g> show parameter log_archive_config;NAME				     TYPE	 VALUE
------------------------------------ ----------- ------------------------------
log_archive_config		     string	 DG_CONFIG=(ora11g,dgora11g,sbora11g)

7、切换后验证

–主库插入测试数据

sys@sbora11g > create table tt0809 as select * from dba_objects;Table created.

–两备库查询

sys@ora11g> select count(*) from tt0809;COUNT(*)
----------86266
sys@dgora11g> select count(*) from tt0809;  COUNT(*)
----------86266

至此主从切换已完成，新主库应与两从库正常同步

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