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The software which [[Oracle Corporation]] markets as '''Oracle Data Guard''' forms an extension to the [[Oracle Database|Oracle
Oracle provides both [[graphical user interface
Data Guard supports both '''physical standby''' and '''logical standby''' sites. Oracle Corporation makes Data Guard available only as a [[product bundling|bundled]] feature included within its "Enterprise Edition" of the [[Oracle RDBMS]].<ref>http://download.oracle.com/docs/cd/B28359_01/server.111/b28294/standby.htm#insertedID3 ''Data Guard Concepts and Administration'', 11g Release 1 (11.1); Section 2.3.2: "Oracle Software Requirements" Retrieved 2007-10-01</ref>
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== Configurations ==
For the purposes of Data Guard, each Oracle database functions either in a primary database role or in a standby database role - with the ability to transition from one role to the other.<ref>{{cite book|url=http://docs.oracle.com/cd/E11882_01/server.112/e41134/concepts.htm#i1033808|title=Oracle Data Guard Concepts and Administration 11g Release 2 (11.2)|last=Rich|first=Kathy
</ref>
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|page= 128
|isbn= 9781467896214
|
|quote= [...] a new identifier DBID is assigned to the new database unless the database is a standby database. In this case it retains the same DBID as the source database.
}}
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| url = http://www.databasejournal.com/features/oracle/article.php/3860251/Leveraging-Logical-Standby-Databases-in-Oracle-11g-Data-Guard.htm
| title = Leveraging Logical Standby Databases in Oracle 11g Data Guard
|
| last = Czuprynski
| first = Jim
|date=January 2010
▲}}</ref> Physical standby may not be appropriate in such a case.
=== Active Data Guard ===
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| title = Oracle Database Options
| url = http://download.oracle.com/docs/cd/B28359_01/license.111/b28287/options.htm#sthref21
| work = Oracle Database Licensing Information 11g Release 1 (12c)
| publisher = Oracle Corporation
| date = January 2009
▲| accessdate = 2009-04-22
| quote = If a physical standby database in a Data Guard configuration has any of the above features enabled, then the Active Data Guard option must be licensed for every such physical standby, and also for the primary database.
}}</ref> extends Oracle Data Guard functionality in Oracle 11g configurations. It allows read-only access on the Physical standby node at the same time as applying archived transactions from the primary node. Also it features Automatic Block Repair and Fast Incremental Backup on Physical Standby,<ref name="Oracle Active data Guard">
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| publisher = Oracle Corporation
| date = January 2010
▲| accessdate = 2009-04-22
| quote = Oracle Active Data Guard enables read-only access to a physical standby database for queries, sorting, reporting, web-based access, etc., while continuously applying changes received from the production database.
}}</ref>
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| url = http://www.oracle.com/technology/deploy/availability/pdf/MAA_WP_10gR2_DataGuardNetworkBestPractices.pdf
| title = Data Guard Redo Transport & Network Best Practices: Oracle Database 10g Release 2
|
| last = Smith
| first = Michael T
|date= February 2007
| format = PDF
| publisher = Oracle Corporation
| pages = 6, 14
| quote = ... sending processes (LNS and ARC) on the production database....The Data Guard LNS process on the production database performs a network send to the Data Guard RFS process on the standby database.
}}</ref> where the '''RFS''' (remote file server) background process within the Oracle instance performs the task of receiving archived redo logs originating from the primary database and writing them to a standby redo log (SRL).<ref>
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| last = Ault
| first = Mike
|
| series = Oracle In-Focus Series
| others = Madhu Tumma
| title = Oracle 10g Grid & Real Application Clusters: Oracle 10g Grid Computing with RAC
| url = https://books.google.
|
| year = 2004
| publisher = Rampant TechPress
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|page= 320
|isbn= 9781430244295
|
|quote= [...] with Oracle 10g, [u]sing standby redo logs on the standby database server, the redo stream arriving on the destination could be applied to the standby database immediately, without having to wait for the standby redo log to be archived and applied.
}}
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| title = Oracle Database 10g Linux administration
| url = https://books.google.com/books?id=2ImPFP6Yk64C
|
| year = 2005
| publisher = McGraw-Hill Professional
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== Advantages ==
Data Guard provides [[high availability]] for a database system. It can also reduce the human intervention required to switch between [[databases]] at [[IT disaster recovery|disaster-recovery]] ("failover") or [[upgrade]]/[[Preventive maintenance|maintenance]] ("switchover") time.
Through the use of standby redo log files, Data Guard can minimize data loss.<ref>
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It supports heterogeneous configurations in which the primary and standby systems may have different CPU architectures, operating systems (for example, Microsoft Windows and Linux), operating-system binaries (32-bit/64-bit), or Oracle database binaries (32-bit/64-bit).<ref name="Data Guard Operational Prerequisites">
{{cite web
| title = Data Guard Operational Prerequisites
| url = http://docs.oracle.com/cd/E11882_01/server.112/e10700/standby.htm#i58150
| work = Data Guard Concepts and Administration
| publisher = Oracle Corporation
▲| accessdate = 2013-08-26
| quote = As of Oracle Database 11g, Data Guard provides increased flexibility for Data Guard configurations in which the primary and standby systems may have different CPU architectures, operating systems (for example, Windows & Linux), operating system binaries (32-bit/64-bit), or Oracle database binaries (32-bit/64-bit).
}}</ref>
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If the network link connecting primary and standby is over-subscribed, the redo logs are not shipped in chronological order, which can result in large gaps appearing in the available redo at the standby. Such a condition results in the standby being behind the primary.
<ref name="Oracle Database Options"/> This can be overcome, using Oracle’ Active Data Guard Farsync technology.
The same release of Oracle Database Enterprise Edition must be installed on the primary database and all standby databases, except during rolling database upgrades using logical standby databases.
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