Oracle9i includes many new features to improve data protection. In addition to significant enhancements to the existing (physical) Standby product, a new logical Standby capability is included, along with a framework that provides monitoring, automation and control for both logical and physical features. The new logical standby database converts redo log files into SQL statements for reapplication to a standby database. This reduces the risk of corruption propagation to the standby, and allows reports to be run concurrently on the standby database with logical log application. It also allows additional indexes and materialized views to be created on the standby to speed up reporting.
Many of the tasks associated with managing a standby database are also automated, including initial instantiation, failover, and graceful primary-to-secondary switch-over and switch back. Administrators can also optionally specify the log apply delay by which each standby site lags the production environment (for increased protection from human errors or corruption's), and choose a zero-loss mode in which redo logs are synchronously sent to the standby site.
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