Data Guard broker considerations for cascaded standby databases in 11.2
Last updated on MAY 16, 2017
Applies to:Oracle Database - Enterprise Edition - Version 18.104.22.168 to 22.214.171.124 [Release 11.2]
Information in this document applies to any platform.
To reduce the load on your primary system, or to reduce the bandwidth requirements imposed when your standbys are separated from the primary database through a Wide Area Network (WAN), you can implement cascaded destinations, whereby a standby database receives its redo data from another standby database, instead of directly from the primary database. In a Data Guard configuration using a cascaded destination, a physical standby database can forward the redo data it receives from the primary database to another standby database. Only a physical standby database can be configured to forward redo data to another standby database. Neither a logical standby database or a snapshot standby database can forward redo to another standby database.
In 11.2 when a cascaded destination is defined on a physical standby database, the physical standby will forward redo it receives from the primary to a second standby database after its standby redo log becomes full and is archived. Thus, the second standby database receiving the forwarded redo as a result of a cascaded destination will necessarily lag behind the primary database. In addition, there is no Data Guard broker support for handling cascaded destinations. In 12c it is now possible to cascade a Standby Database in Real-Time, ie. the first Standby Database can send Redo from the Standby RedoLogs to the cascaded Standby Database. Also, the Data Guard Broker now supports cascaded standby databases using the RedoRoutes database configuration property. For complete information on 12c Data Guard broker RedoRoutes property and cascaded standby databases refer to the following MAA whitepaper:
While the 11.2 Data Guard does not support cascaded standby databases it is still possible to utilize the broker with some additional manual configuration. The following procedure describes the additional considerations for an 11.2 broker configuration with cascaded standby databases.
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