Oracle Data Guard can be deployed to maintain standby databases at a secondary site. These standby databases are maintained as synchronized copies of the production database.
If the production database becomes unavailable because of a planned or an unplanned outage, Data Guard can switch the standby database to the production role, thus minimizing the downtime associated with the outage, and preventing any data loss.
The ability to create standby databases was first offered as a feature in Oracle 8i, although users were creating manual standby databases since Oracle 7.3.
Features introduced in Oracle 8i
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Read-only physical standby database
Managed recovery of standby
Remote archiving of redo log files
Features introduced in Oracle 9i
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Integrated zero-data-loss capability
Data Guard Broker w/ Data Guard Manager GUI
Command Line Interface (CLI)
Switchover and Failover operations
Automatic gap resolution
Automatic Synchronization
Logical standby databases
Maximum protection / availability
Enhanced Data Guard Broker
Cascaded redo log destinations
Features introduced in Oracle 10g
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Real-time apply
Recovery through OPEN RESETLOGS
Simplified configuration with VALID_FOR attribute
Standby redo log support on logical standby databases
Improved redo transmission security
Improved support for RAC
Zero downtime instantiation of logical standby databases
Fast-start Failover
Flashback Database across Data Guard switchovers
Asynchronous Redo Transmission
Faster Redo Apply failover
Features introduced with Oracle 11g
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Standby databases can remain open while doing recovery
Heterogeneous platform support (standby can be on a different platform). For example, production on Linux and standby on Windows.
