Oracle Data Guard Broker Switchover and Failover

Perform smooth switchover and failover with Data Guard Broker.

Let’s look at how to perform oracle data guard switchover / failover using broker configuration. It’s very simple to perform switchover / failover using data guard broke as its only one single command that does the work.

Data Guard Broker Switchover
Data Guard Broker Failover

Data Guard Broker Switchover

A database can be in one of two mutually exclusive modes (primary or standby). These roles can be altered at run-time without loss of data or resetting of redo logs. This process is known as a Switchover and can be performed using the following commands.

Switchover Using DGMGRL

Consider proddb and proddb_st as primary and standby databases respectively. Connect to DGMGRL and issue below command

On primary:
===========
dgmgrl sys/sys@proddb

DGMGRL> show configuration;

DGMGRL> SWITCHOVER TO proddb_st;
Performing switchover NOW, please wait...
Operation requires a connection to instance "proddb_st" on database "proddb_st"
Connecting to instance "proddb_st"...
Connected.
New primary database "proddb_st" is opening...
Operation requires startup of instance "proddb" on database "proddb"
Starting instance "proddb"...
ORACLE instance started.
Database mounted.
Switchover succeeded, new primary is "proddb_st"

DGMGRL> show configuration;

Revert Back Using DGMGRL

Once you perform switchover, the original primary becomes standby and original standby becomes primary. At this point, our primary is proddb_st and standby is proddb. Connect to current primary proddb_st and switchover to current stnadby proddb

On current primary(proddb_st):
==============================
dgmgrl sys/sys@proddb_st

DGMGRL> show configuration;

DGMGRL> switchover to proddb;
Performing switchover NOW, please wait...
Operation requires a connection to instance "proddb" on database "proddb"
Connecting to instance "proddb"...
Connected.
New primary database "proddb" is opening...
Operation requires startup of instance "proddb_st" on database "proddb_st"
Starting instance "proddb_st"...
ORACLE instance started.
Database mounted.
Switchover succeeded, new primary is "proddb"

DGMGRL> show configuration;

Data Guard Broker Failover

A failover is when you have lost primary database. It’s very simple to perform failover using data guard broker.

Crash Primary Database (Simulate)
Failover to Standby
Rebuild Primary After Failover

Crash Primary Database (Simulate)

Let us simulate failure. We will kill the PMON process at OS level on primary

On primary:
===========
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

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:
===========
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):
===============================
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" succeeded

Verify 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):
===========================
select name,open_mode from v$database;
select process, status, sequence# from v$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):
===============================
dgmgrl sys/sys@proddb_st
DGMGRL> switchover to proddb;

Enjoy!