Oracle Learning Dataguard (II) DG Architecture-Application Services

Dataguard provides two different ways to apply logs to the standby database: Redo apply (physical standby), SQL apply (logical standby).

The main goal of DG is to protect database data from loss. Another goal is to provide a high degree of isolation between master and slave libraries.

Physical Standby:

Redo apply uses the method of media recovery, reads the Redo record from the SRL in memory, and then applies the change vectors directly to recover the data from the library. The master and slave libraries are physical copies of block-to-block. Media recovery can restore data concurrently to provide higher performance. In the 11g, the recovery of the physical standby can only be performed in the Mount state, so the physical standby cannot provide query functionality. 11G introduced the active DataGuard. Use the database to open the database only if the log is applied. Provides a read-only query for the business. DG not only protects data, but also provides read-only queries, which improves the efficiency of system use.

This article is from the "Ding Dong" blog, please be sure to keep this source http://lqding.blog.51cto.com/9123978/1681204

Oracle Learning Dataguard (II) DG Architecture-Application Services