Enable Dataguard Broker and Configuring its component DGMGRL

Data Guard Configurations and Broker Configurations:

A Data Guard configuration consists of one primary database and up to nine standby databases. The databases in a Data Guard configuration are connected by Oracle Net and may be dispersed geographically. There are no restrictions on where the databases are located as long as they can communicate with each other. For example, you can have a standby database on the same system as the primary database, along with two standby databases on another system.

The Data Guard broker logically groups these primary and standby databases into a broker configuration that allows the broker to manage and monitor them together as an integrated unit. You can manage a broker configuration using either the Oracle Enterprise Manager graphical user interface or the Data Guard command-line interface.

Role Transitions-Swithover and Failover

A database operates in one of the following mutually exclusive roles: primary or standby. Data Guard enables you to change these roles dynamically by issuing the SQL statements or by using either of the Data Guard broker's interfaces. Oracle Data Guard supports the following role ransitions:

Convert Physical standby to Snap shot standby database

Snap Shot Standby database ( 11gR2 Feature ):

-- A physical standby database which is in OPEN ( READ WRITE ) mode is called as Snap Shot Standby datase.

-- We can convert the physical standby to Snap shot standby database.

-- Advantage of Snap shot standby is that We don't require an another server to create a clone database. Some standby database can be used as a clone database by converting it into Snap shot standby database.

Convert Physical standby to Active standby database

Active Standby database ( 11gR1 Feature):

-- A physical standby database which is in OPEN READ ONLY mode is called as Active Standby database.

-- We can convert the Physical standby to Logical standby as below

-- STEP1: Stop the MRP

-- STEP2:  Open the database in read only mode

-- STEP3:  Start the MRP 

-- Advantage of Active Data guard is standby can serve the DRL ( SELECT ) statements , while currently being synchronized with the primary by the MRP.