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ORACLE 10g
DATA GUARD BROKER
Ritesh Chhajer
Sr. Oracle DBA
Agenda
DG Broker Concepts & Advantages
Setup using CLI(DGMGRL)
Useful broker commands
Switchover
Concepts

Any Data Guard configuration consists of one primary database and up to nine standby databases.

The Data Guard broker logically groups these primary and standby databases into a broker
configuration so as to manage and monitor them together as an integrated unit.

Data Guard broker is a centralized framework to manage entire Data Guard configuration through
a client connection to any database in the configuration.

Accessed either locally or remotely using either of the two clients: CLI interface(DGMGRL) or the
Data Guard page from GUI( OEM Grid Control )

DGMGRL does not have the ability to create standby (GUI can do it). CLI is used mostly for
configuration and management.

Easy switchover/failover with one command thereby minimizing overall downtime associated with
the planned/unplanned outage

Integrated with CRS so that database role changes occur smoothly and seamlessly.

Instead of managing primary and standby databases with various SQL*Plus statements, broker
provides a single unified configuration
DMON
 Data Guard monitor process (DMON) runs for every database
instance that is managed by the broker and maintains the broker
configuration in a binary configuration file
Whenever a broker command is issued, DMON process:
 Carries out the request on primary database
 Coordinates with DMON process for each of the other databases
 Updates its local configuration file
 Communicates with DMON process for each of the other databases
to update their copies of the configuration file
Prerequisites
Set up following parameters on primary and standby:
DG_BROKER_START=TRUE
DG_BROKER_CONFIG_FILE1=‘<PATH>’
DG_BROKER_CONFIG_FILE2=‘<PATH>’
LOCAL_LISTENER
GLOBAL_DBNAME in listener.ora as db_unique_name_DGMGRL.db_domain

To enable DGMGRL to restart instances, a service with a specific name must be statically
registered with the local listener of each instance.

For RAC, ensure dg_broker_config_files are on shared storage and accessible to all instances.

START_OPTIONS for RAC database must be set to MOUNT in OCR using SRVCTL (For
switchover/Failover operations for broker and CRS to coordinate while restarting instances and
database role reversal)

SPFILE must be used
Switchover
Once SWITCHOVER is issued, the broker does the following:
1.
Verifies state of primary and standby database are enabled and in ONLINE state
2.
Shuts down all RAC instances except one
3.
Switches roles between the primary and standby databases.
4.
Updates the broker configuration file to record the changes in roles
5.
Restarts the new standby database and any RAC instances that were shutdown prior to
switchover.
6.
Restarts the new primary database, opens it in read-write mode, and starts log transport services
transmitting redo data to the archived redo log files for standby database
7.
After switchover completes, the overall Data Guard protection mode remains at the same
protection level as it was before the switchover.
8.
For DGMGRL to restart instances automatically, you must connect to the database as SYSDBA
using the username and password specified in the remote password file before beginning the
switchover.
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