Oracle Data Guard an Overview

Introduction to Oracle Data Guard

Oracle Data Guard ensures high availability, data protection, and disaster recovery for enterprise data. Oracle Data Guard maintains a transactionally consistent copy of the primary database known as physical standby database to achieve high availability, data protection, and disaster recovery.
The primary & standby databases can be either a single-instance Oracle database or an Oracle Real Application Clusters (Oracle RAC) database. A primary database can support up to 30 standby databases.
The Standby databases may be dispersed geographically and are connected by Oracle Net. The Standby databases are synchronized with the primary database using oracle log transport and redo apply services.

Types of standby database in oracle

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. Most widely used type of standby database.

Logical standby database: Contains the same logical information as the production database, although the physical organization and structure of the data can be different.

Snapshot Standby Database: The physical standby database can be temporarily converted to a snapshot standby database, Snapshot Standby Database is best used in scenarios that require a temporary,updatable snapshot of a physical standby database. The redo data received by a snapshot standby database is not applied until the snapshot standby is converted back into a physical standby database. The local changes made in snapshot standby database is discarded as soon as it is converted back to physical standby database.

Far Sync Instances: An Oracle Data Guard far sync instance is a remote Oracle Data Guard destination that accepts redo from the primary database and then ships that redo to other members of the Oracle Data Guard configuration. A far sync instance only requires initfile, password file and controlfile. It does not have any datafile. It receives redo into standby redo logs (SRLs), and archives those SRLs to local archived redo logs and then ships that redo to other members of the Oracle Data Guard configuration
NOTE: Far sync instances are part of the Oracle Active Data Guard Far Sync feature, which requires an Oracle Active Data Guard license.

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How to Power On/off Oracle Exadata Machine

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ORA-28374: typed master key not found in wallet

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ORA-16905: The member was not enabled yet

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How to Switch Log File from All Instances in RAC

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Starting RMAN and connecting to Database

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ORA-46655: no valid keys in the file from which keys are to be imported

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