Switchover to a Physical Standby using the Data Guard Command Line Interface

The Data Guard Command Line Interface can be used to manage your Data Guard environment through the command line. Using the Data Guard Command Line Interface, dgmgrl, you can manage the broker configuration along with the configurations of the databases configured in the broker.

This document will detail a switchover using the Data Guard Command Line Interface. If you would like to see the steps for switchover using a manual method see the post Data Guard Switchover to a Physical Standby. For information on performing a switchover using Oracle Enterprise Manager see the post Switchover to a Physical Standby using Oracle Enterprise Manager 11gR1 Grid Control

Switchover Process

During the switchover to a physical standby the broker performs the following:

1. Verifies that the primary is enabled and is in the TRANSPORT-ON state and that the target standby database is enabled and is in the APPLY-ON state.

2. Shuts down all instances on the primary except for one if needed. No instances will be shutdown on the target physical standby.

3. The primary database is first transitioned to the standby role then the original standby is transitioned to the primary role.

4. The broker configuration file is updated to reflect the change in roles.

5. Restarts the new standby database and begins the redo apply service.

6. The new primary database is opened in read/wirte mode and the redo transport service is started.

Below we connect to primary database using dgmgrl and display the configuration.

[oracle@prod ~]$ dgmgrl
DGMGRL for Linux: Version 11.2.0.1.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
DGMGRL> connect sys
Password:
Connected.
DGMGRL>

Show the configuration

DGMGRL> show configuration

Configuration - proddb

  Protection Mode: MaxPerformance
  Databases:
    proddb  - Primary database
    standby - Physical standby database

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS

DGMGRL>

The command SWITCHOVER TO < standby database name > is used to perform the switchover operation.

DGMGRL> switchover to standby;
Performing switchover NOW, please wait...
New primary database "standby" is opening...
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.
Switchover succeeded, new primary is "standby"
DGMGRL> 

Note: You might run into the following error during your switchover when attempting to start the new standby database.

Database dismounted.
ORACLE instance shut down.
Operation requires startup of instance "proddb" on database "proddb"
Starting instance "proddb"...
Unable to connect to database
ORA-12514: TNS:listener does not currently know of service requested in connect descriptor

Failed.
Warning: You are no longer connected to ORACLE.

Please complete the following steps to finish switchover:
        start up and mount instance "proddb" of database "proddb"

DGMGRL>

The problem is that the Data Guard Broker is attempting to connect to a service called < sid >_DGMGRL or in this case proddb_DGMGRL. If you are receiving the error you can exit out of the dgmgrl and mount the new standby to complete to the switchover. To prevent this problem in the future add a static registration for < sid >_DGMMGRL to your ORACLE_HOME/network/admin/listener.ora. Below is an example.

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (GLOBAL_DBNAME = proddb_DGMGRL)
      (ORACLE_HOME = /u01/app/oracle/product/11.2.0/dbhome_1)
      (SID_NAME = proddb)
    )
  )
 

A quick show configuration will show that standby is the primary and proddb is the physical standby.

DGMGRL> show configuration;

Configuration - proddb

  Protection Mode: MaxPerformance
  Databases:
    standby - Primary database
    proddb  - Physical standby database

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS

DGMGRL> 

In order to switch back to the original primary database all you need to do is perform the switchover command on the new primary database as detailed below.

[oracle@dreco admin]$ dgmgrl
DGMGRL for Linux: Version 11.2.0.1.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
DGMGRL> connect sys
Password:
Connected.
DGMGRL> show configuration;

Configuration - proddb

  Protection Mode: MaxPerformance
  Databases:
    standby - Primary database
    proddb  - Physical standby database

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS

DGMGRL> switchover to proddb;
Performing switchover NOW, please wait...
New primary database "proddb" is opening...
Operation requires shutdown of instance "standby" on database "standby"
Shutting down instance "standby"...
ORA-01109: database not open

Database dismounted.
ORACLE instance shut down.
Operation requires startup of instance "standby" on database "standby"
Starting instance "standby"...
ORACLE instance started.
Database mounted.
Switchover succeeded, new primary is "proddb"
DGMGRL>

Performing a switchover using the Data Guard Command Line interface is a simple and efficient process. However, if you are managing your Data Guard environment with Oracle Enterprise Manager Grid Control you will need to reconfigure the monitoring and metrics for the new primary and standby.