Dataguard的switchover 和failover 并将老主库flashback 成standby库

Dataguard中的role transition：switchover和failover以及将failover后的old primary flackback成physical standby库
 
Dataguard中的role transition包括两种：switchover和failover,
区别在于：switchover将一个physical standby database switchover成为primary database过程可以保证无数据丢失，在完成后其它的standby数据库和原来的primary库还可以成为这个dataguard的standby role的一部分.
Failover当主库crash无法正常启动时，将一个standby库failover成primary role库，如果在primary库在出故障之前不是处于protection的话，将会有一些数据丢失，因为当前在写的 redo没有办法传到standby库。如果primary，standby库都打开了flashback的话，可以将原来的主库重新设为新primary role数据库的standby库。
在进行role transition要检查：
primary,standby是否处于archvielog模式。
Standby库的tempory file要和primary匹配是rac的话：在standby RAC上只有一个实例mount,其它都要关闭
 
 COLUMN NAME FORMAT A18
 COLUMN VALUE FORMAT A16
COLUMN TIME_COMPUTED FORMAT A24
SELECT * FROM V$DATAGUARD_STATS;---可以从这张视图看到没有应用的日志应用上去要多长时间
SQL> SELECT * FROM V$DATAGUARD_STATS;
 
NAME              VALUE           UNIT                          TIME_COMPUTED
------------------ ---------------- ------------------------------ ------------------------
apply finish time +00 00:38:57.2  day(2) to second(1) interval  26-SEP-2008 23:16:39
apply lag         +00 09:48:00    day(2) to second(0) interval  26-SEP-2008 23:16:39
estimated startup 25              second                        26-SEP-2008 23:16:39
time
 
standby has been o N                                              26-SEP-2008 23:16:39
pen
 
transport lag     +00 00:00:00    day(2) to second(0) interval  26-SEP-2008 23:16:39
 
SQL> select NAME ,DB_UNIQUE_NAME ,open_mode,DATABASE_ROLE from v$database;
 
一．Switchovers的过程：


1.      检查主库目前的状态：
SQL> SELECT SWITCHOVER_STATUS FROM V$DATABASE;
 
SWITCHOVER_STATUS
--------------------
TO STANDBY
2.将主库置为standby role
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 mount;
ORACLE instance started.
 
Total System Global Area 218103808 bytes
Fixed Size                 1260984 bytes
Variable Size            117441096 bytes
Database Buffers          96468992 bytes
Redo Buffers               2932736 bytes
Database mounted.
 
2.      standby库转为primary
 
SQL> select NAME ,DB_UNIQUE_NAME ,open_mode,DATABASE_ROLE from v$database;
 
 
SQL> SELECT SWITCHOVER_STATUS FROM V$DATABASE;
 
SWITCHOVER_STATUS
--------------------
TO PRIMARY
 
SQL> alter database commit to switchover to primary;
 
Database altered.
 
SQL> alter database open;
 
Database altered.
SQL> select NAME ,DB_UNIQUE_NAME ,open_mode,DATABASE_ROLE from v$database;
 
NAME              DB_UNIQUE_NAME                OPEN_MODE DATABASE_ROLE
------------------ ------------------------------ ---------- ----------------
MAINDB            standb                        READ WRITE PRIMARY
 
主库上：
SQL> alter database recover managed standby database disconnect from session;
 
Database altered.
 
SQL> select NAME ,DB_UNIQUE_NAME ,open_mode,DATABASE_ROLE from v$database;
 
NAME              DB_UNIQUE_NAME                OPEN_MODE DATABASE_ROLE
------------------ ------------------------------ ---------- ----------------
MAINDB            maindb                        MOUNTED   PHYSICAL STANDBY
 
 
 
二．Failovers的过程：
 
查询没有应用的日志：
SQL> SELECT THREAD#, LOW_SEQUENCE#, HIGH_SEQUENCE# FROM V$ARCHIVE_GAP;
THREAD# LOW_SEQUENCE# HIGH_SEQUENCE#
  Cp过来并register
SQL> ALTER DATABASE REGISTER PHYSICAL LOGFILE 'filespec1';
 
  SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE FINISH FORCE;
 
SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY;
 
SQL> ALTER DATABASE OPEN;
 
 
 
 
 
一旦主数据故障无法使用，就可以迅速激活镜像备份：
　　1、如果可能，归档主服务器当前重做日志，传送到镜像服务器；
　　2、使用主服务器的归档日志文件做恢复：
　　SQL>recover standby database;
　　3、激活并打开数据库：
　　SQL>alter database activate standby database;
　　SQL>alter database mount;
　　SQL>alter database open;
 
三．将Failover之后的老的主库 flashback成新primary的standby库：
1．  在新主库查出failover时的SCN：


SQL> SELECT TO_CHAR(STANDBY_BECAME_PRIMARY_SCN) FROM V$DATABASE;
 
TO_CHAR(STANDBY_BECAME_PRIMARY_SCN)
----------------------------------------
172313
 
2．  在old primary库上：
SQL> SHUTDOWN IMMEDIATE;
SQL> STARTUP MOUNT;
SQL> FLASHBACK DATABASE TO SCN172313;
 
SQL> ALTER DATABASE CONVERT TO PHYSICAL STANDBY;
 
SQL> SHUTDOWN IMMEDIATE;
SQL> STARTUP MOUNT;
 
SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE
 USING CURRENT LOGFILE DISCONNECT;
 
 
 
 
12.4.1Flashing Back a Failed Primary Database into a Physical Standby Database
The following steps assume the user has already performed a failover involving a
physical standby database and Flashback Database has been enabled on the old
primary database. This procedure brings the old primary database back into the Data
Guard configuration as a new physical standby database.
Step 1 Determine the SCN at which the old standby database became the
primary database.
On the new primary database, issue the following query to determine the SCN at
which the old standby database became the new primary database:
SQL> SELECT TO_CHAR(STANDBY_BECAME_PRIMARY_SCN) FROM V$DATABASE;
Step 2 Flash back the failed primary database.
To create a new physical standby database, shut down the old primary database (if
necessary), mount it, and flash it back to the value forSTANDBY_BECAME_PRIMARY_
SCNthat was determined in Step 1:
SQL> SHUTDOWN IMMEDIATE;
SQL> STARTUP MOUNT;
SQL> FLASHBACK DATABASE TO SCNstandby_became_primary_scn;
Step 3 Convert the database to a physical standby database.
Perform. the following steps on the old primary database:
1.Issue the following statement on the old primary database:
SQL> ALTER DATABASE CONVERT TO PHYSICAL STANDBY;
This statement will dismount the database after successfully converting the control
file to a standby control file.
2.Shut down and restart the database:
SQL> SHUTDOWN IMMEDIATE;
SQL> STARTUP MOUNT;
Step 4 Restart transporting redo to the new physical standby database.
Before the new standby database was created, the new primary database probably
stopped transmitting redo to the remote destination. To restart redo transport services,
perform. the following steps on the new primary database:
1.Issue the following query to see the current state of the archive destinations:
SQL> SELECT DEST_ID, DEST_NAME, STATUS, PROTECTION_MODE, DESTINATION, ERROR,SRL
 FROM V$ARCHIVE_DEST_STATUS;
2.If necessary, enable the destination:
SQL> ALTER SYSTEM SET LOG_ARCHIVE_DEST_STATE_n=ENABLE;
See Also:Oracle Data Guard Broker for automatic reinstatement of
the failed primary database as a new standby database (as an
alternative to using Flashback Database)
Using Flashback Database After a Failover
Data Guard Scenarios12-25