Data Guard Broker switchover Tips Oracle Database Tips by Donald BurlesonDecember 9, 2015

Oracle Data Guard Broker

Role Transition using Data Guard Broker

Role transition is a complicated activity in a Data Guard environment. Data Guard broker has significantly simplified the task of switchover and failover by internally combining the steps required to transition a standby database into the primary role. Role transition management using Data Guard manager's CLI interface is identical in both Oracle9i and Oracle10g. This section will present the switchover and failover operation using CLI commands.

Data Guard Broker

Switchover Operation

In order to switchover a Oracle instance to the primary role and vice-versa, the following pre-requisites should be met before issuing the SWITCHOVER command:

• The intended state of the primary database should be READ-WRITE-XPTON for Oracle9i and ONLINE for Oracle10g.
   

• The intended state of the target physical Oracle instance should be PHYSICAL-APPLY-ON for Oracle9i, and ONLINE for Oracle10g.
   

• If the target standby database is a logical standby database, its intended state should be LOGICAL-APPLY-ON for Oracle9i, and ONLINE for Oracle10g.
   

• There should be no blocking error on the participating standby database. Usually, the blocking issues are any error in log management services or data file identifications. If the broker finds any blocking issues, it terminates the switchover operation leaving the primary and standby databases in their original state.

These pre-requisites are no different than the requirements for manually switching over a standby and primary database.

To switchover a standby database into the primary role, execute the following statement. It can be executed in the CLI environment after connecting to the primary database or the target Oracle instance using an account having SYSDBA privilege.

SWITCHOVER TO 'stdbydb';

Broker

Switchover Operation

The broker will restart the primary and Oracle instance after the switchover. In some cases, usually due to privilege or incorrect setting of initialization parameters, the broker may not be able to restart the databases. In those circumstances, the database needs to be manually started after the switchover operation is complete. Then, run the SHOW SITE command to verify the state and role of the databases after the switchover operation.

Failover Operation

The first step in a failover operation is to evaluate the best available Oracle instance for failover. This is explained in Chapter 6, "Switchover and Failover". The FAILOVER command should be executed on the Oracle instance that is selected for the failover operation. The GRACEFUL or FORCED keyword can be used with the FAILOVER command. GRACEFUL failover is always preferred in order to minimize any data loss.

FAILOVER TO 'stdbydb' GRACEFUL;

Data Guard broker will restart the new primary database. After the failover, the appropriate SHOW commands should be executed in order to validate the failover operation.

Managing Data Protection Modes

From previous chapters, a Data Guard configuration must have a defined protection mode. By default, the protection mode of a configuration is MAXIMUM PERFORMANCE. In order to change the protection mode of a configuration, execute the following steps: