Agents are deployed on both the production and
standby database, and a Data Guard Broker coordinates commands. A single Data
Guard command invokes the eight steps required for failover.
In addition to providing physical standby database support, Data Guard can create a
logical standby database. In this scenario, Oracle archive logs are transformed into
SQL transactions and applied to an open standby database.
Oracle Database 10g introduced several new features, including support for real-time
application of redo data, integration with the Flashback database feature, and
archivelog compression. Starting with Oracle Database 10g, rolling upgrades are
supported. As of Oracle Database 11g, the Active Data Guard Opton enables the
standby database to be used for queries, sorting, and reporting even as changes from
the production system are being applied.
Fail Safe
The Fail Safe feature provides a higher level of reliability for an Oracle database.
Failover is implemented through a second system or node that provides access to
data residing on a shared disk when the first system or node fails.
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