有客户使用本地和公有云通过vpn搭建数据库容灾,其中有一个需求,当本地环境出现问题云端容灾库接管业务,当本地环境恢复之后,本地继续做为主库,云端作为备库.我这里使用oracle dataguard结合flashback模拟实现客户需求(也可以在failover之后通过重新搭建dg实现类似需求,具体需要看客户的实际场景:数据量,带宽,恢复时间,技术能力等)
正常dg同步的主备环境
这里ora11g主机是主库,ora10g主机是备库

--数据库版本
SQL> select * from v$version;
BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
PL/SQL Release 11.2.0.4.0 - Production
CORE    11.2.0.4.0      Production
TNS for Linux: Version 11.2.0.4.0 - Production
NLSRTL Version 11.2.0.4.0 - Production
---主库(ora11g)
SQL> select open_mode,database_role,(select HOST_NAME from v$instance) HOST_NAME,flashback_on from v$database;
OPEN_MODE                      DATABASE_ROLE                  HOST_NAME                      FLASHBACK_
------------------------------ ------------------------------ ------------------------------ ----------
READ WRITE                     PRIMARY                        ora11g                         YES
SQL> create  table xff.t_xifenfei as select * from dba_objects;
Table created.
SQL> select count(*) from xff.t_xifenfei;
  COUNT(*)
----------
     86348
---备库(ora10g)
SQL> select open_mode,database_role,(select HOST_NAME from v$instance) HOST_NAME,flashback_on from v$database;
OPEN_MODE                      DATABASE_ROLE                  HOST_NAME                      FLASHBACK_
------------------------------ ------------------------------ ------------------------------ ----------
READ ONLY WITH APPLY           PHYSICAL STANDBY               ora10g                         YES
SQL> select count(*) from xff.t_xifenfei;
  COUNT(*)
----------
     86348

模拟主库(ora11g)故障,直接激活备库(ora10g)
模拟dg备库(ora10g)直接failover操作

SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL;
Database altered.
SQL> ALTER DATABASE ACTIVATE PHYSICAL STANDBY DATABASE;
Database altered.

Sat Mar 24 16:05:40 2017
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL
MRP0: Background Media Recovery cancelled with status 16037
Errors in file /u01/app/oracle/diag/rdbms/ora11g/ora11g/trace/ora11g_pr00_13428.trc:
ORA-16037: user requested cancel of managed recovery operation
Managed Standby Recovery not using Real Time Apply
Recovery interrupted!
Recovered data files to a consistent state at change 1470499
Sat Mar 24 16:05:40 2017
MRP0: Background Media Recovery process shutdown (ora11g)
Managed Standby Recovery Canceled (ora11g)
Completed: ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL
Sat Mar 24 16:05:50 2017
ALTER DATABASE ACTIVATE PHYSICAL STANDBY DATABASE
ALTER DATABASE ACTIVATE [PHYSICAL] STANDBY DATABASE (ora11g)
All dispatchers and shared servers shutdown
CLOSE: killing server sessions.
CLOSE: all sessions shutdown successfully.
Sat Mar 24 16:05:50 2017
SMON: disabling cache recovery
Killing 3 processes with pids 13372,13393,13388 (all RFS) in order to
    disallow current and future RFS connections. Requested by OS process 13350
Begin: Standby Redo Logfile archival
End: Standby Redo Logfile archival
RESETLOGS after incomplete recovery UNTIL CHANGE 1470499
Archived Log entry 9 added for thread 1 sequence 14 ID 0xfd5a5fc1 dest 1:
Resetting resetlogs activation ID 4250558401 (0xfd5a5fc1)
Online log /u01/app/oracle/oradata/ora11g/redo01.log: Thread 1 Group 1 was previously cleared
Online log /u01/app/oracle/oradata/ora11g/redo02.log: Thread 1 Group 2 was previously cleared
Online log /u01/app/oracle/oradata/ora11g/redo03.log: Thread 1 Group 3 was previously cleared
Standby became primary SCN: 1470497
Sat Mar 24 16:05:52 2017
Setting recovery target incarnation to 4
ACTIVATE STANDBY: Complete - Database mounted as primary
Completed: ALTER DATABASE ACTIVATE PHYSICAL STANDBY DATABASE

模拟新主库（ora10g）业务操作

SQL> select open_mode,database_role,(select HOST_NAME from v$instance) HOST_NAME,flashback_on from v$database;
OPEN_MODE                      DATABASE_ROLE                  HOST_NAME                      FLASHBACK_
------------------------------ ------------------------------ ------------------------------ ----------
MOUNTED                        PRIMARY                        ora10g                         YES
SQL> alter database open;
Database altered.
SQL>  select open_mode,database_role,(select HOST_NAME from v$instance) HOST_NAME,flashback_on from v$database;
OPEN_MODE                      DATABASE_ROLE                  HOST_NAME                      FLASHBACK_
------------------------------ ------------------------------ ------------------------------ ----------
READ WRITE                     PRIMARY                        ora10g                         YES
SQL> alter system switch logfile;
System altered.
SQL> /
System altered.
SQL> /
/
System altered.
SQL>
System altered.
SQL>
SQL> archive log list;
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     5
Next log sequence to archive   7
Current log sequence           7
SQL> delete from xff.t_xifenfei;
86348 rows deleted.
SQL> commit;
Commit complete.
SQL> select count(*) from xff.t_xifenfei;
  COUNT(*)
----------
         0

原主库(ora11g)配置为新备库

---原主库(ora10g)
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.
Total System Global Area 3056513024 bytes
Fixed Size                  2257152 bytes
Variable Size             704646912 bytes
Database Buffers         2332033024 bytes
Redo Buffers               17575936 bytes
Database mounted.
SQL> Flashback database to scn 1470490;
Flashback complete.
SQL> select open_mode,database_role,(select HOST_NAME from v$instance) HOST_NAME,flashback_on from v$database;
OPEN_MODE                      DATABASE_ROLE                  HOST_NAME                      FLASHBACK_
------------------------------ ------------------------------ ------------------------------ ----------
MOUNTED                        PRIMARY                        ora11g                         YES
--现在主库(ora10g)
SQL> alter database create standby controlfile as '/tmp/ctl.3';
Database altered.
[oracle@ora10g ~]$ scp /tmp/ctl.3 192.168.222.11:/u01/app/oracle/oradata/ora11g/control01.ctl
oracle@192.168.222.11's password:
ctl.3
--现在备库(ora11g)
SQL> shutdown abort
ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.
Total System Global Area 3056513024 bytes
Fixed Size                  2257152 bytes
Variable Size             704646912 bytes
Database Buffers         2332033024 bytes
Redo Buffers               17575936 bytes
Database mounted.
SQL> col open_mode for a30
SQL> col database_role for a30
SQL> col HOST_NAME for a30
SQL> col flashback_on for a10
SQL> set lines 150
SQL> select open_mode,database_role,(select HOST_NAME from v$instance) HOST_NAME,flashback_on from v$database;
OPEN_MODE                      DATABASE_ROLE                  HOST_NAME                      FLASHBACK_
------------------------------ ------------------------------ ------------------------------ ----------
MOUNTED                        PHYSICAL STANDBY               ora11g                         NO
SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT  LOGFILE DISCONNECT FROM SESSION;
Database altered.

Sat Mar 24 16:10:09 2017
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT  LOGFILE DISCONNECT FROM SESSION
Attempt to start background Managed Standby Recovery process (ora11g)
Sat Mar 24 16:10:09 2017
MRP0 started with pid=27, OS id=27086
MRP0: Background Managed Standby Recovery process started (ora11g)
 started logmerger process
Sat Mar 24 16:10:14 2017
Managed Standby Recovery starting Real Time Apply
Parallel Media Recovery started with 4 slaves
Media Recovery start incarnation depth : 1, target inc# : 4, irscn : 1470499
Waiting for all non-current ORLs to be archived...
All non-current ORLs have been archived.
Clearing online redo logfile 1 /u01/app/oracle/oradata/ora11g/redo01.log
Clearing online log 1 of thread 1 sequence number 7
Clearing online redo logfile 1 complete
Clearing online redo logfile 2 /u01/app/oracle/oradata/ora11g/redo02.log
Clearing online log 2 of thread 1 sequence number 8
Completed: ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT  LOGFILE DISCONNECT FROM SESSION
Clearing online redo logfile 2 complete
Clearing online redo logfile 3 /u01/app/oracle/oradata/ora11g/redo03.log
Clearing online log 3 of thread 1 sequence number 9
Clearing online redo logfile 3 complete
Media Recovery Waiting for thread 1 sequence 13 branch(resetlogs_id) 854379205
Sat Mar 24 16:10:16 2017
RFS[3]: Assigned to RFS process 27098
RFS[3]: Opened log for thread 1 sequence 13 dbid 48871109 branch 854379205
Archived Log entry 2 added for thread 1 sequence 13 rlc 854379205 ID 0xfd5a5fc1 dest 2:
Sat Mar 24 16:10:16 2017
RFS[4]: Assigned to RFS process 27100
RFS[4]: Opened log for thread 1 sequence 14 dbid 48871109 branch 854379205
Archived Log entry 3 added for thread 1 sequence 14 rlc 854379205 ID 0xfd5a5fc1 dest 2:
RFS[3]: Opened log for thread 1 sequence 1 dbid 48871109 branch 947798452
RFS[4]: Opened log for thread 1 sequence 3 dbid 48871109 branch 947798452
Sat Mar 24 16:10:16 2017
RFS[5]: Assigned to RFS process 27070
RFS[5]: Opened log for thread 1 sequence 2 dbid 48871109 branch 947798452
Archived Log entry 4 added for thread 1 sequence 1 rlc 947798452 ID 0x2ec1ed0 dest 2:
Archived Log entry 5 added for thread 1 sequence 3 rlc 947798452 ID 0x2ec1ed0 dest 2:
RFS[3]: Opened log for thread 1 sequence 4 dbid 48871109 branch 947798452
RFS[4]: Opened log for thread 1 sequence 5 dbid 48871109 branch 947798452
Archived Log entry 6 added for thread 1 sequence 5 rlc 947798452 ID 0x2ec1ed0 dest 2:
Archived Log entry 7 added for thread 1 sequence 4 rlc 947798452 ID 0x2ec1ed0 dest 2:
Archived Log entry 8 added for thread 1 sequence 2 rlc 947798452 ID 0x2ec1ed0 dest 2:
RFS[4]: Opened log for thread 1 sequence 6 dbid 48871109 branch 947798452
Archived Log entry 9 added for thread 1 sequence 6 rlc 947798452 ID 0x2ec1ed0 dest 2:
RFS[3]: Opened log for thread 1 sequence 7 dbid 48871109 branch 947798452
Archived Log entry 10 added for thread 1 sequence 7 rlc 947798452 ID 0x2ec1ed0 dest 2:
Media Recovery Log /u01/app/oracle/fast_recovery_area/ORA11GDG/archivelog/2017_03_24/o1_mf_1_13_9xmyh8cs_.arc
Media Recovery Log /u01/app/oracle/fast_recovery_area/ORA11GDG/archivelog/2017_03_24/o1_mf_1_14_9xmyh8dr_.arc
Media Recovery Log /u01/app/oracle/fast_recovery_area/ORA11GDG/archivelog/2017_03_24/o1_mf_1_1_9xmyh8fk_.arc
Media Recovery Log /u01/app/oracle/fast_recovery_area/ORA11GDG/archivelog/2017_03_24/o1_mf_1_2_9xmyh8fo_.arc
Media Recovery Log /u01/app/oracle/fast_recovery_area/ORA11GDG/archivelog/2017_03_24/o1_mf_1_3_9xmyh8fm_.arc
Media Recovery Log /u01/app/oracle/fast_recovery_area/ORA11GDG/archivelog/2017_03_24/o1_mf_1_4_9xmyh8g3_.arc
Media Recovery Log /u01/app/oracle/fast_recovery_area/ORA11GDG/archivelog/2017_03_24/o1_mf_1_5_9xmyh8g4_.arc
Media Recovery Log /u01/app/oracle/fast_recovery_area/ORA11GDG/archivelog/2017_03_24/o1_mf_1_6_9xmyh8gs_.arc
Media Recovery Log /u01/app/oracle/fast_recovery_area/ORA11GDG/archivelog/2017_03_24/o1_mf_1_7_9xmyh8hl_.arc
Media Recovery Log /u01/app/oracle/fast_recovery_area/ORA11GDG/archivelog/2017_03_24/o1_mf_1_8_9xmy5d3f_.arc
Media Recovery Waiting for thread 1 sequence 9 (in transit)
Recovery of Online Redo Log: Thread 1 Group 4 Seq 9 Reading mem 0
  Mem# 0: /u01/app/oracle/oradata/ora11g/std_redo10.log

SQL>  ALTER DATABASE RECOVER MANAGED STANDBY DATABASE cancel;
Database altered.
SQL> alter database open;
Database altered.
SQL>  ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT  LOGFILE DISCONNECT FROM SESSION;
Database altered.
SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE cancel;
Database altered.
SQL> alter database flashback on;
Database altered.
SQL> select open_mode,database_role,(select HOST_NAME from v$instance) HOST_NAME,flashback_on from v$database;
OPEN_MODE                      DATABASE_ROLE                  HOST_NAME                      FLASHBACK_
------------------------------ ------------------------------ ------------------------------ ----------
READ ONLY                      PHYSICAL STANDBY               ora11g                         YES
SQL> select count(*) from xff.t_xifenfei;
  COUNT(*)
----------
         0
--现在主库
SQL> drop table xff.t_xifenfei ;
Table dropped.
SQL> select count(*) from xff.t_xifenfei;
select count(*) from xff.t_xifenfei
                         *
ERROR at line 1:
ORA-00942: table or view does not exist
--现在备库
SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT  LOGFILE DISCONNECT FROM SESSION;
Database altered.
SQL> select open_mode,database_role,(select HOST_NAME from v$instance) HOST_NAME,flashback_on from v$database;
OPEN_MODE                      DATABASE_ROLE                  HOST_NAME                      FLASHBACK_
------------------------------ ------------------------------ ------------------------------ ----------
READ ONLY WITH APPLY           PHYSICAL STANDBY               ora11g                         YES
SQL> select count(*) from xff.t_xifenfei;
select count(*) from xff.t_xifenfei
                         *
ERROR at line 1:
ORA-00942: table or view does not exist

通过上述一系列操作,以前假设故障的主库,现在变成了被failover激活的主库的备库,也就是说数据库主备关系由ora11g主库—>ora10g备库变成了ora10g主库—>ora11g备库

switchover实现主备库互换

---现在主库(ora10g)
SQL>  ALTER DATABASE COMMIT TO SWITCHOVER TO STANDBY WITH SESSION SHUTDOWN;
Database altered.
--现在备库(ora11g)
SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY WITH SESSION SHUTDOWN;
Database altered.
SQL>  select open_mode,database_role,(select HOST_NAME from v$instance) HOST_NAME,flashback_on from v$database;
OPEN_MODE                      DATABASE_ROLE                  HOST_NAME                      FLASHBACK_
------------------------------ ------------------------------ ------------------------------ ----------
MOUNTED                        PRIMARY                        ora11g                         YES
SQL> alter database open;
Database altered.
SQL> select open_mode,database_role,(select HOST_NAME from v$instance) HOST_NAME,flashback_on from v$database;
OPEN_MODE                      DATABASE_ROLE                  HOST_NAME                      FLASHBACK_
------------------------------ ------------------------------ ------------------------------ ----------
READ WRITE                     PRIMARY                        ora11g                         YES
--最新备库(ora10g)
SQL> startup
ORACLE instance started.
Total System Global Area 3056513024 bytes
Fixed Size                  2257152 bytes
Variable Size             687869696 bytes
Database Buffers         2348810240 bytes
Redo Buffers               17575936 bytes
Database mounted.
Database opened.
SQL>  ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT  LOGFILE DISCONNECT FROM SESSION;
Database altered.
SQL> select open_mode,database_role,(select HOST_NAME from v$instance) HOST_NAME,flashback_on from v$database;
OPEN_MODE                      DATABASE_ROLE                  HOST_NAME                      FLASHBACK_
------------------------------ ------------------------------ ------------------------------ ----------
READ ONLY WITH APPLY           PHYSICAL STANDBY               ora10g                         YES
--最新主库(ora11g)
SQL> alter system switch logfile;
System altered.
SQL> create table t_xifenfei as select * from dba_objects;
Table created.
SQL> select count(*) from t_xifenfei;
  COUNT(*)
----------
     86347
--最新备库(ora10g)
SQL>  select count(*) from t_xifenfei;
  COUNT(*)
----------
     86347

通过switchover主备库再次互换由ora10g主库—>ora11g备库变成了ora11g主库—>ora10g备库,再次恢复到最初的状态.这个不是唯一的方法,可以通过重建dg,也能够实现类似需求.