【DATAGUARD】實體dg的switchover切換（五）
<a href="http://s3.51cto.com/wyfs02/M01/70/49/wKioL1W14ojj46gNAAFA3YCtmjE441.jpg"></a>
各位技術愛好者，看完本文後，你可以掌握如下的技能，也可以學到一些其它你所不知道的知識，~O(∩_∩)O~：
① 實體dg的switchover切換演練過程
② 實體dg管理和維護的一些sql
注意：本篇BLOG中代碼部分需要特别關注的地方我都用***背景和紅色字型來表示，比如下邊的例子中，thread 1的最大歸檔日志号為33，thread 2的最大歸檔日志号為43是需要特别關注的地方。
List of Archived Logs in backup set 11
Thrd Seq Low SCN Low Time Next SCN Next Time
---- ------- ---------- ------------------- ---------- ---------
1 32 1621589 2015-05-29 11:09:52 1625242 2015-05-29 11:15:48
1 33 1625242 2015-05-29 11:15:48 1625293 2015-05-29 11:15:58
2 42 1613951 2015-05-29 10:41:18 1625245 2015-05-29 11:15:49
2 43 1625245 2015-05-29 11:15:49 1625253 2015-05-29 11:15:53
本文如有錯誤或不完善的地方請大家多多指正，ITPUB留言或QQ皆可，您的批評指正是我寫作的最大動力。
項目
主庫
dg庫
db 類型
單執行個體
db version
11.2.0.3
db 存儲
FS type
ORACLE_SID
oradg11g
oradgphy
db_name
主機IP位址：
192.168.59.130
OS版本及kernel版本
RHEL6.5 64位，2.6.32-504.16.2.el6.x86_64
OS hostname
rhel6_lhr
1．角色
Oracle 資料庫中含有兩種角色。
使用者角色：定義了一組權限的集合，該角色可以配置設定給使用者，也可以配置設定給其他角色。
資料庫角色：在備庫中資料庫扮演什麼樣的角色，primary還是standby。
v$database.DATABASE_ROLE辨別了資料庫的運作角色。
處于備庫環境中，資料庫有兩種類型：phsical standby、logical standby。
2．角色管理服務
一個資料庫運作在如下互相排斥的角色中。
Primary role：一個資料庫運作在primary role，那麼log transport services傳遞重做日志到備庫。
Standby role：一個資料庫運作在standby role，那麼log apply services應用歸檔日志到備庫。
角色管理服務允許使用者動态地在主、備庫中進行角色切換。
使用者可以使用角色管理服務，進行主、備庫的計劃中的角色切換，這個叫switchover，或者是非計劃中的角色切換，叫failover。
3．Switchover&Failover
切換是在主資料庫與其備資料庫之間進行角色反轉，切換確定不丢失資料。這是對于主系統計劃維護的典型操作。在切換期間，主資料庫轉換到備角色，備資料庫轉換到主角色。轉換發生不需要重建任何資料庫。
（1）Switchover
用到的場景：計劃中的角色轉換或使用者作業系統和硬體的維護等。
（2）Failover
故障轉移是當主資料庫不可用時執行的。故障轉移隻有在主資料庫災難故障的情況下執行，并且故障轉移導緻備資料庫轉換到主角色。用到的場景：非計劃中的角色切換，一般在緊急情況下使用。根據保護模式的不同，可能會沒有或者很少的資料損失。
（3）角色轉換決策樹
角色轉換（switchover&failover）的最終目的是盡快地使主庫線上，而同時盡量減少資料損失或者是實作無資料損失。盡量選擇當機時間最短，同時資料損失最小的政策。總之在失敗切換前，應該先考慮修複主資料庫或者進行無資料損失的角色轉換。
即使使用無資料損失的備庫方案，修複主庫可能會比切換到備庫更快點。如果修複了主庫，那麼就不需要修改用戶端的連接配接。但是如果修複工作導緻了任何的資料損失，那麼可能需要重新建立所有的備用資料庫。
通常情況下，最合适切換的備庫為已經應用了最多的歸檔日志的備用資料庫。
① 主庫和實體dg的switchover切換
② 還原為最初始的狀态
一.4.2.1 主庫oradg11g的參數設定檢查
這裡主要有2個内容需要檢測：
① fal_client、fal_server、standby_file_management、db_file_name_convert 、log_filename_convert是否合理
② standbylog file 是否已經建立
[oracle@rhel6_lhr ~]$ echo $ORACLE_SID
[oracle@rhel6_lhr ~]$
[oracle@rhel6_lhr ~]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.3.0 Production on 星期日 7月 26 17:33:53 2015
Copyright (c) 1982, 2011, Oracle. All rights reserved.
連接配接到:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
17:33:53 SQL> col name format a25
17:33:55 SQL> col VALUE format a20
17:33:55 SQL> SELECT a.NAME,a.VALUE
17:33:55 2 FROM v$parameter a
17:33:55 3 WHERE a.NAME LIKE '%file_name_convert'
17:33:55 4 OR a.NAME LIKE 'fal%'
17:33:55 5 OR a.NAME LIKE 'standby_file%';
NAME VALUE
------------------------- --------------------
db_file_name_convert oradgphy, oradg11g
log_file_name_convert oradgphy, oradg11g
fal_client oradg11g
fal_server oradgphy
standby_file_management AUTO
已用時間: 00: 00: 00.01
17:33:56 SQL>
20:32:09 SQL> set line 9999 pagesize 9999
20:36:47 SQL> col db_id format a15
20:36:47 SQL> select GROUP#, DBID db_id, THREAD#, SEQUENCE#, BYTES, USED, ARCHIVED, STATUS, FIRST_CHANGE#, NEXT_CHANGE#,LAST_CHANGE# from v$standby_log ;
GROUP# DB_ID THREAD# SEQUENCE# BYTES USED ARC STATUS FIRST_CHANGE# NEXT_CHANGE# LAST_CHANGE#
---------- --------------- ---------- ---------- ---------- ---------- --- ---------- ------------- ------------ ------------
4 UNASSIGNED 1 0 52428800 0 YES UNASSIGNED
5 UNASSIGNED 1 0 52428800 0 YES UNASSIGNED
6 UNASSIGNED 0 0 52428800 0 YES UNASSIGNED
7 UNASSIGNED 0 0 52428800 0 YES UNASSIGNED
已用時間: 00: 00: 00.02
20:36:47 SQL> select * from v$logfile;
GROUP# STATUS TYPE MEMBER IS_
---------- ------- ------- --------------------------------------------------- ---
3 ONLINE /u01/app/oracle/oradata/oradg11g/redo03.log NO
2 ONLINE /u01/app/oracle/oradata/oradg11g/redo02.log NO
1 ONLINE /u01/app/oracle/oradata/oradg11g/redo01.log NO
4 STANDBY /u01/app/oracle/oradata/oradg11g/standby_redo04.log NO
5 STANDBY /u01/app/oracle/oradata/oradg11g/standby_redo05.log NO
6 STANDBY /u01/app/oracle/oradata/oradg11g/standby_redo06.log NO
7 STANDBY /u01/app/oracle/oradata/oradg11g/standby_redo07.log NO
已選擇7行。
已用時間: 00: 00: 00.00
20:37:00 SQL> ! ls /u01/app/oracle/oradata/oradg11g/standby*
/u01/app/oracle/oradata/oradg11g/standby_redo04.log /u01/app/oracle/oradata/oradg11g/standby_redo06.log
/u01/app/oracle/oradata/oradg11g/standby_redo05.log /u01/app/oracle/oradata/oradg11g/standby_redo07.log
20:37:11 SQL>
一.4.2.2 主庫oradg11g執行切換
17:35:45 SQL> select name, LOG_MODE, OPEN_MODE, database_role, SWITCHOVER_STATUS, db_unique_name from v$database;
NAME LOG_MODE OPEN_MODE DATABASE_ROLE SWITCHOVER_STATUS DB_UNIQUE_NAME
--------- ------------ -------------------- ---------------- -------------------- ------------------------------
ORADG11G ARCHIVELOG READ WRITE PRIMARY TO STANDBY oradg11g
17:35:46 SQL> alter database commit to switchover to physical standby with session shutdown;
資料庫已更改。
已用時間: 00: 00: 06.22
17:36:14 SQL> shutdown immediate
ORA-01092: ORACLE instance terminated. Disconnection forced
17:36:35 SQL> ORA-24324: 未初始化服務句柄
ORA-01041: 内部錯誤, hostdef 擴充名不存在
17:36:35 SQL> exit
從 Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options 斷開
SQL*Plus: Release 11.2.0.3.0 Production on 星期日 7月 26 17:36:39 2015
已連接配接到空閑例程。
17:36:39 SQL> startup mount;
ORACLE 例程已經啟動。
Total System Global Area 325685248 bytes
Fixed Size 2228064 bytes
Variable Size 192938144 bytes
Database Buffers 125829120 bytes
Redo Buffers 4689920 bytes
資料庫裝載完畢。
17:36:52 SQL> select name, LOG_MODE, OPEN_MODE, database_role, SWITCHOVER_STATUS, db_unique_name from v$database;
ORADG11G ARCHIVELOG MOUNTED PHYSICAL STANDBY RECOVERY NEEDED oradg11g
17:37:04 SQL>
告警日志：
Sun Jul 26 17:36:07 2015
alter database commit to switchover to physical standby with session shutdown
ALTER DATABASE COMMIT TO SWITCHOVER TO PHYSICAL STANDBY [Process Id: 37669] (oradg11g)
Thread 1 advanced to log sequence 127 (LGWR switch)
Current log# 1 seq# 127 mem# 0: /u01/app/oracle/oradata/oradg11g/redo01.log
Stopping background process CJQ0
Stopping background process QMNC
All dispatchers and shared servers shutdown
CLOSE: killing server sessions.
Active process 37415 user 'grid' program 'oracle@rhel6_lhr'
Active process 37413 user 'grid' program 'oracle@rhel6_lhr'
Active process 37483 user 'oracle' program 'oracle@rhel6_lhr (W000)'
CLOSE: all sessions shutdown successfully.
Waiting for all non-current ORLs to be archived...
Waiting for the ORL for thread 1 sequence 126 to be archived...
Sun Jul 26 17:36:11 2015
Archived Log entry 349 added for thread 1 sequence 126 ID 0x5441e6d9 dest 1:
ORL for thread 1 sequence 126 has been archived...
All non-current ORLs have been archived.
Waiting for all FAL entries to be archived...
All FAL entries have been archived.
Waiting for potential Physical Standby switchover target to become synchronized...
Active, synchronized Physical Standby switchover target has been identified
Switchover End-Of-Redo Log thread 1 sequence 127 has been fixed
Switchover: Primary highest seen SCN set to 0x0.0x1a1f6f
ARCH: Noswitch archival of thread 1, sequence 127
ARCH: End-Of-Redo Branch archival of thread 1 sequence 127
ARCH: LGWR is actively archiving destination LOG_ARCHIVE_DEST_2
ARCH: Standby redo logfile selected for thread 1 sequence 127 for destination LOG_ARCHIVE_DEST_2
Archived Log entry 350 added for thread 1 sequence 127 ID 0x5441e6d9 dest 1:
ARCH: Archiving is disabled due to current logfile archival
Primary will check for some target standby to have received alls redo
Final check for a synchronized target standby. Check will be made once.
LOG_ARCHIVE_DEST_2 is a potential Physical Standby switchover target
Active, synchronized target has been identified
Target has also received all redo
Backup controlfile written to trace file /u01/app/oracle/diag/rdbms/oradg11g/oradg11g/trace/oradg11g_ora_37669.trc
Clearing standby activation ID 1413605081 (0x5441e6d9)
The primary database controlfile was created using the
'MAXLOGFILES 16' clause.
There is space for up to 13 standby redo logfiles
Use the following SQL commands on the standby database to create
standby redo logfiles that match the primary database:
ALTER DATABASE ADD STANDBY LOGFILE 'srl1.f' SIZE 52428800;
ALTER DATABASE ADD STANDBY LOGFILE 'srl2.f' SIZE 52428800;
ALTER DATABASE ADD STANDBY LOGFILE 'srl3.f' SIZE 52428800;
ALTER DATABASE ADD STANDBY LOGFILE 'srl4.f' SIZE 52428800;
Archivelog for thread 1 sequence 127 required for standby recovery
Switchover: Primary controlfile converted to standby controlfile succesfully.
Switchover: Complete - Database shutdown required
Completed: alter database commit to switchover to physical standby with session shutdown
Sun Jul 26 17:36:15 2015
Process (ospid 26918) is suspended due to switchover to physical standby operation.
Sun Jul 26 17:36:33 2015
Performing implicit shutdown abort due to switchover to physical standby
Shutting down instance (abort)
License high water mark = 7
USER (ospid: 37669): terminating the instance
Instance terminated by USER, pid = 37669
Sun Jul 26 17:36:35 2015
Instance shutdown complete
ORA-1092 : opitsk aborting process
Sun Jul 26 17:36:44 2015
Starting ORACLE instance (normal)
****************** Large Pages Information *****************
Total Shared Global Region in Large Pages = 0 KB (0%)
Large Pages used by this instance: 0 (0 KB)
Large Pages unused system wide = 0 (0 KB) (alloc incr 4096 KB)
Large Pages configured system wide = 0 (0 KB)
Large Page size = 2048 KB
RECOMMENDATION:
Total Shared Global Region size is 314 MB. For optimal performance,
prior to the next instance restart increase the number
of unused Large Pages by atleast 157 2048 KB Large Pages (314 MB)
system wide to get 100% of the Shared
Global Region allocated with Large pages
***********************************************************
LICENSE_MAX_SESSION = 0
LICENSE_SESSIONS_WARNING = 0
Picked latch-free SCN scheme 3
Autotune of undo retention is turned on.
IMODE=BR
ILAT =27
LICENSE_MAX_USERS = 0
SYS auditing is disabled
Starting up:
With the Partitioning, OLAP, Data Mining and Real Application Testing options.
ORACLE_HOME = /u01/app/oracle/product/11.2.0/dbhome_1
System name: Linux
Node name: rhel6_lhr
Release: 2.6.32-504.16.2.el6.x86_64
Version: #1 SMP Tue Apr 21 08:37:59 PDT 2015
Machine: x86_64
VM name: VMWare Version: 6
Using parameter settings in server-side spfile /u01/app/oracle/product/11.2.0/dbhome_1/dbs/spfileoradg11g.ora
System parameters with non-default values:
processes = 150
sga_target = 312M
control_files = "/u01/app/oracle/oradata/oradg11g/control01.ctl"
control_files = "/u01/app/oracle/flash_recovery_area/oradg11g/control02.ctl"
db_file_name_convert = "oradgphy"
db_file_name_convert = "oradg11g"
log_file_name_convert = "oradgphy"
log_file_name_convert = "oradg11g"
db_block_size = 8192
compatible = "11.2.0.0.0"
log_archive_dest_1 = "LOCATION=USE_DB_RECOVERY_FILE_DEST db_unique_name=oradg11g valid_for=(ALL_LOGFILES,ALL_ROLES)"
log_archive_dest_2 = "SERVICE=tns_oradgphy LGWR ASYNC db_unique_name=oradgphy valid_for=(ONLINE_LOGFILES,PRIMARY_ROLE)"
log_archive_dest_3 = "SERVICE=tns_oradglg LGWR ASYNC db_unique_name=oradglg valid_for=(ONLINE_LOGFILES,PRIMARY_ROLE)"
log_archive_dest_4 = "SERVICE=tns_oradgss LGWR ASYNC db_unique_name=oradgss valid_for=(ONLINE_LOGFILES,PRIMARY_ROLE)"
log_archive_dest_state_1 = "ENABLE"
log_archive_dest_state_2 = "ENABLE"
log_archive_dest_state_3 = "defer"
log_archive_dest_state_4 = "defer"
fal_client = "oradg11g"
fal_server = "oradgphy"
log_archive_config = "DG_CONFIG=(oradg11g,oradgphy,oradglg,oradgss)"
log_archive_max_processes= 6
db_recovery_file_dest = "/u01/app/oracle/flash_recovery_area"
db_recovery_file_dest_size= 4122M
standby_file_management = "AUTO"
undo_tablespace = "UNDOTBS1"
remote_login_passwordfile= "EXCLUSIVE"
db_domain = ""
dispatchers = "(PROTOCOL=TCP) (SERVICE=oradg11gXDB)"
audit_file_dest = "/u01/app/oracle/admin/oradg11g/adump"
audit_trail = "DB"
db_name = "oradg11g"
db_unique_name = "oradg11g"
open_cursors = 300
pga_aggregate_target = 78M
diagnostic_dest = "/u01/app/oracle"
Sun Jul 26 17:36:45 2015
PMON started with pid=2, OS id=37709
PSP0 started with pid=3, OS id=37711
Sun Jul 26 17:36:46 2015
VKTM started with pid=4, OS id=37713 at elevated priority
VKTM running at (1)millisec precision with DBRM quantum (100)ms
GEN0 started with pid=5, OS id=37717
這一步容易出現問題，注意下邊的問題：
alter database commit to switchover to physical standby with session shutdown;
稍等。。。。等待資料庫挂掉後再啟動到mount，千萬别shutdown immediate,應該用shutdown abort，等待告警日志中出現如下提示再進行下一步操作，否則可能導緻switchover切換失敗，主庫将不可用
--Switchover: Primary controlfile converted to standby controlfile succesfully.
--Switchover: Complete - Database shutdown required
--Completed: alter database commit to switchover to physical standby with session shutdown
--Sun Jul 26 17:36:15 2015
--Process (ospid 26918) is suspended due to switchover to physical standby operation.
一.4.2.3 備庫oradgphy執行切換
[oracle@rhel6_lhr admin]$ echo $ORACLE_SID
[oracle@rhel6_lhr admin]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.3.0 Production on 星期日 7月 26 17:40:24 2015
17:40:24 SQL> select name, LOG_MODE, OPEN_MODE, database_role, SWITCHOVER_STATUS, db_unique_name from v$database;
ORADG11G ARCHIVELOG READ ONLY WITH APPLY PHYSICAL STANDBY TO PRIMARY oradgphy
17:40:28 SQL> alter database commit to switchover to primary with session shutdown;
已用時間: 00: 00: 02.07
17:40:44 SQL> select name, LOG_MODE, OPEN_MODE, database_role, SWITCHOVER_STATUS, db_unique_name from v$database;
ORADG11G ARCHIVELOG MOUNTED PRIMARY NOT ALLOWED oradgphy
17:40:56 SQL>
17:42:47 SQL> alter database open;
已用時間: 00: 00: 01.88
17:43:04 SQL>
Sun Jul 26 17:40:42 2015
alter database commit to switchover to primary with session shutdown
ALTER DATABASE SWITCHOVER TO PRIMARY (oradgphy)
Maximum wait for role transition is 15 minutes.
Switchover: Media recovery is still active
Role Change: Canceling MRP - no more redo to apply
Sun Jul 26 17:40:44 2015
MRP0: Background Media Recovery cancelled with status 16037
Errors in file /u01/app/oracle/diag/rdbms/oradgphy/oradgphy/trace/oradgphy_pr00_28229.trc:
ORA-16037: user requested cancel of managed recovery operation
Managed Standby Recovery not using Real Time Apply
Recovery interrupted!
MRP0: Background Media Recovery process shutdown (oradgphy)
Role Change: Canceled MRP
SMON: disabling cache recovery
Backup controlfile written to trace file /u01/app/oracle/diag/rdbms/oradgphy/oradgphy/trace/oradgphy_ora_37868.trc
SwitchOver after complete recovery through change 1711983
Online log /u01/app/oracle/oradata/oradgphy/redo01.log: Thread 1 Group 1 was previously cleared
Online log /u01/app/oracle/oradata/oradgphy/redo02.log: Thread 1 Group 2 was previously cleared
Online log /u01/app/oracle/oradata/oradgphy/redo03.log: Thread 1 Group 3 was previously cleared
Standby became primary SCN: 1711981
AUDIT_TRAIL initialization parameter is changed back to its original value as specified in the parameter file.
Switchover: Complete - Database mounted as primary
Completed: alter database commit to switchover to primary with session shutdown
Sun Jul 26 17:41:14 2015
idle dispatcher 'D000' terminated, pid = (17, 1)
一.4.2.4 新備庫oradg11g開啟實時應用
SQL*Plus: Release 11.2.0.3.0 Production on 星期日 7月 26 17:45:47 2015
17:45:47 SQL> select name, LOG_MODE, OPEN_MODE, database_role, SWITCHOVER_STATUS, db_unique_name from v$database;
17:45:53 SQL> alter database recover managed standby database using current logfile disconnect;
已用時間: 00: 00: 06.02
17:46:13 SQL> alter database recover managed standby database cancel;
已用時間: 00: 00: 01.48
17:46:16 SQL> alter database open;
已用時間: 00: 00: 00.56
17:46:21 SQL> alter database recover managed standby database using current logfile disconnect;
17:46:35 SQL>
一.4.2.5 測試切換後的情況
17:47:42 SQL> select name, LOG_MODE, OPEN_MODE, database_role, SWITCHOVER_STATUS, db_unique_name from v$database;
NAME LOG_MODE OPEN_MODE DATABASE_ROLE SWITCHOVER_STATUS DB_UNIQUE_
--------- ------------ -------------------- ---------------- -------------------- ----------
ORADG11G ARCHIVELOG READ WRITE PRIMARY TO STANDBY oradgphy
17:47:54 SQL> create table test as select * from scott.emp;
表已建立。
已用時間: 00: 00: 00.86
17:48:21 SQL> select count(1) from test;
COUNT(1)
----------
14
17:50:27 SQL>
17:50:27 SQL> conn sys/lhr@tns_oradg11g as sysdba
已連接配接。
17:50:42 SQL> select count(1) from test;
17:50:46 SQL> conn sys/lhr@tns_oradgphy as sysdba
17:51:08 SQL> drop table test;
表已删除。
已用時間: 00: 00: 01.14
17:51:13 SQL> conn sys/lhr@tns_oradgphy as sysdba
17:51:17 SQL> conn sys/lhr@tns_oradg11g as sysdba
17:51:21 SQL> select count(1) from test;
select count(1) from test
*
第 1 行出現錯誤:
ORA-00942: 表或視圖不存在
17:51:24 SQL>
一.4.2.6 切換回原來最初的狀态
新主庫ordgphy操作：
20:28:43 SQL> alter database commit to switchover to physical standby with session shutdown;
已用時間: 00: 00: 04.65
20:30:01 SQL> shutdown immediate
20:30:33 SQL> startup mount;
ORA-24324: 未初始化服務句柄
20:30:41 SQL> exit
SQL*Plus: Release 11.2.0.3.0 Production on 星期日 7月 26 20:30:45 2015
20:30:45 SQL> startup mount;
Total System Global Area 242171904 bytes
Fixed Size 2227256 bytes
Variable Size 188744648 bytes
Database Buffers 46137344 bytes
Redo Buffers 5062656 bytes
新備庫oradg11g操作：
20:28:46 SQL> select name, LOG_MODE, OPEN_MODE, database_role, SWITCHOVER_STATUS, db_unique_name from v$database;
ORADG11G ARCHIVELOG READ ONLY WITH APPLY PHYSICAL STANDBY TO PRIMARY oradg11g
20:31:20 SQL> alter database commit to switchover to primary with session shutdown;
20:31:32 SQL> alter database open;
已用時間: 00: 00: 00.34
20:31:38 SQL> select name, LOG_MODE, OPEN_MODE, database_role, SWITCHOVER_STATUS, db_unique_name from v$database;
ORADG11G ARCHIVELOG READ WRITE PRIMARY RESOLVABLE GAP oradg11g
oradgphy 操作：
20:30:54 SQL> alter database recover managed standby database using current logfile disconnect;
已用時間: 00: 00: 06.04
20:32:23 SQL> alter database recover managed standby database cancel;
已用時間: 00: 00: 01.01
20:32:36 SQL> alter database open;
已用時間: 00: 00: 00.21
20:32:42 SQL> alter database recover managed standby database using current logfile disconnect;
20:32:53 SQL> 20:32:53 SQL> select name, LOG_MODE, OPEN_MODE, database_role, SWITCHOVER_STATUS, db_unique_name from v$database;
ORADG11G ARCHIVELOG READ ONLY WITH APPLY PHYSICAL STANDBY NOT ALLOWED oradgphy
20:33:21 SQL>
OK，切換完成。
切換過程中尤其注意主庫執行alter database commit to switchover to physical standby with session shutdown;後需要等待資料庫abort掉，或者我們手動的shutdown abort，否則可能導緻實驗失敗，主庫脫離dg環境不可用進而變為了failover切換了，是以實驗之前還是對主庫做rman備份比較穩妥一些。
進行Dataguard switchover和failover是非常常見的運維需求，在實際場景下，我們盡可能選擇穩妥完全的政策進行操作，SQL指令還是我們比較好的選擇，多操作幾次就熟悉了。
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本文作者：小麥苗，隻專注于資料庫的技術，更注重技術的運用
QQ：642808185 若加QQ請注明你所正在讀的文章标題
創作時間地點：2015-07-26 09:00~ 2015-07-27 19:00 于唐鎮金唐較高價的電梯大廈宿舍
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本文轉自lhrbest 51CTO部落格，原文連結：http://blog.51cto.com/lhrbest/1678769，如需轉載請自行聯系原作者