What is Oracle Data Guard?

Oracle Data Guard provides high availability, data protection and disaster recovery for enterprise data. This is achieved by creating and administrating one or more Standby databases to survive Oracle Production data during disasters and data corruptions.

Data Guard maintains the standby database as the transactionally-consistent copy of the Production database

As the Oracle Database versions evolved, additional Oracle Data Guard features were implemented along with that of in the previous version. Below is the list of it.

ORACLE 7.3

®     Feature Name: Standby database

®     Manual transfer and apply of archived redo logs

ORACLE 8i

®     Read-Only Standby Database

®     Managed recovery

®     Remote archiving redo log files

®     Tablespace and datafiles operations NOT replicated

®     Introduction of “Data Guard” technology - a collection of Unix shell scripts, such as dgdeploy.sh which deployed the Data Guard configuration of the primary and standby databases

ORALCE 9i

®      “Data Guard” promoted to be a part of Oracle Kernel

®     “Zero Data Loss” Integration

®     Data Guard Broker and Data Guard Manager GUI

®     Switchover and Failover operations

®     Automatic synchronous

®     Auto datafile and tablespace operations

®     Gap detection & resolution

®     Delay option

®     Parallel recovery

ORACLE 9iR2

®     Logical Standby Database

®  Protection modes: Maximum Protection, Maximum Availability and Maximum Performance

®     Cascade Standby database

ORACLE 10g

®     Real-Time Apply

®     Flashback database

ORACLE 10gR2

®     Fast-Start Failover

®     Guaranteed restore point

®     Asynchronous redo transfer

ORACLE 11g

®     Active Standby Database (Active Data Guard)

®     Snapshot Standby

®     Compress Redo traffic

®     Rolling upgrade with transient Logical Standby

®     Heterogeneous platform support (Production –Linux, Standby – Windows)

®     Lost-write detection

®     Block Change Tracking on Standby database

ORACLE11gR2

®     Automatic Block Corruption Repair

ORACLE 12c

®     Far Sync

®     Fast Sync

®     Real-time cascading

®     SYSDG User and role

Possible Number of Standby databases:

In Oracle 8i               -         Up to 4 Standby databases

In Oracle 9i               -         Up to 9 Standby databases

In Oracle 10g            -         Up to 9 Standby databases

In Oracle 11g             -         Up to 30 Standby databases

In Oracle 12c             -         Up to 30 Standby databases

Advantages:

Ø  Oracle Data Guard provides High Availability for a database system.

Ø  With Data Guard, we can improve the Production database performance by offloading resource-intensive backup and reporting operations to the Standby systems.

Ø  If there is a planned or unplanned outage on the Production database, then Data Guard can switch any of the Standby database to the Production role (either manually or automatically), minimizing the downtime associated with the outage.

Ø  The Standby databases in Oracle Data Guard can be dispersed geographically connected by Oracle Net.

Disadvantages:

Ø  Oracle Data Guard is available only with Oracle Database Enterprise Edition as an additional feature.