Data Guard Broker Failover
It’s very simple to perform failover using data guard broker. If primary database is unavailable, we can activate standby using below method.
Note: A failover is when you have lost primary database.
Crash Primary database
Let us simulate failure. We will kill the PMON process at OS level on primary
On primary:
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[oracle@prod admin]$ ps -ef|grep pmon
grid 2636 1 0 Apr15 ? 00:00:12 asm_pmon_+ASM
oracle 16914 1 0 14:03 ? 00:00:00 ora_pmon_proddb
oracle 17722 15893 0 15:08 pts/0 00:00:00 grep pmon
[oracle@prod admin]$ kill -9 16914 Failover to Standby
Connect to standby database proddb_st (as primary crashed or not available) and failover to standby proddb_st
On standby:
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dgmgrl sys/sys@proddb_st
DGMGRL> show configuration;
DGMGRL> FAILOVER TO proddb_st;
Performing failover NOW, please wait...
Failover succeeded, new primary is "proddb_st"
DGMGRL> show configuration;Rebuild Primary After Failover
Post failover, there are two methods of rebuilding your failed primary
Method 1: Rebuild from scratch –> RMAN duplicate
Method 2: Flashback database –> only if Flashback was enabled
Reinstate failed primary: When you use data guard broker, with just one command, the primary can be rebuilt. Start the failed primary server, in this case start proddb server
On current primary (proddb_st):
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dgmgrl sys/sys@proddb_st
DGMGRL> show configuration;
DGMGRL> reinstate database proddb;
Reinstating database "proddb", please wait...
Operation requires shutdown of instance "proddb" on database "proddb"
Shutting down instance "proddb"...
ORA-01109: database not open
Database dismounted.
ORACLE instance shut down.
Operation requires startup of instance "proddb" on database "proddb"
Starting instance "proddb"...
ORACLE instance started.
Database mounted.
Continuing to reinstate database "proddb" ...
Reinstatement of database "proddb" succeededVerify proddb post reinstate: The best part is broker will automatically recover earlier failed primary proddb, mount the database and start MRP too
On failed primary (proddb):
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sqlplus / as sysdba
SQL> select name,open_mode from v$database;
SQL> select process, status, sequence# from v$managed_standby;Switchover to get original configuration: At this stage, you can perform switchover to again get back original configuration
On current primary (proddb_st):
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dgmgrl sys/sys@proddb_st
DGMGRL> switchover to proddb;