Backing up an Oracle Data Guard environment

Oracle Data Guard Overview
Data Guard enables and automates the management of a disaster recovery solution for Oracle databases
located on the same campus or across the continent. Data Guard consists of a production database
(also
known as the primary database) and one or more standby database
(s) , which are consistent copies of the
production database.
A standby database can be either a physical standby database or a logical standby database. A physical
standby database provides a physically identical copy of the primary database, with on-disk database
structures that are identical to the primary database on a block-for-block basis. The database schema,
including indexes, is the same. A physical standby database is kept synchronized with the primary
database by recovering the redo data received from the primary database.
A logical standby database contains the same logical information as the production database, although
the physical organization and structure of the data can be different. It is kept synchronized with the primary
database by transforming the data in the redo logs received from the primary database into SQL
statements and then executing the SQL statements on the standby database. A logical standby database
can be used for other business purposes in addition to disaster recovery requirements.
Network
Production
Database
Logical Standby
Database
Open for
Reports
SQL
Apply
Transform
Redo to SQL
Physical Standby
Database
DIGITAL DATA STORAGE
DIGITAL DATA STORAGE
Backup
Redo Apply
Sync or Async
Redo Shipping
... up to 9 Standby
Databases supported
Figure 2 Oracle Data Guard with Physical and Logical Standby database
Oracle Data Guard offers two easy-to-use methods to handle planned and unplanned outages of the
production site. The methods are called switchover and failover, which can be easily initiated directly
through SQL.
Switchover
The switchover is a planned role reversal of the primary and standby databases, to handle planned
maintenance on the primary database. A switchover operation does not require re-instantiation of the
database. This allows the primary database to assume the role of a standby database almost
immediately. As a result, scheduled maintenance can be performed more easily and frequently. For
example, switchover may be used to perform an upgrade on the primary site by switching over all of
the database clients to the standby.
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