The objective of the Standby Database feature is to support the capability of maintaining a duplicate, or standby, database of a primary, or on-line, database for recovering from disasters at the production site. The Standby Database consists of an external interface and checks within the Oracle kernel code to detect and correct data corruption situations.
Using the Standby Database, availability is increased by providing production applications accessibility to their data through a switch over to the standby database sooner than if the usual recovery procedures are applied to the primary database.
The Standby Database feature allows you to maintain a duplicate copy of a database at a remote site by using the archived log information. The database being copied from is referred to as the primary database, and the database being copied to, or the duplicate copy, is referred to as the standby database.
The primary database is any Oracle database functioning as accustomed, without restriction. The standby database is duplicated on physical hardware (disk and cpu) separate from the primary database and is not used for any application other than as a disaster recovery system. The standby database is kept constantly in recovery mode.
As the primary database archives its redo logs, these log files can be transferred to the remote site and applied to the standby database. The standby database is always behind in time and transactional history from the primary database.
In the event of a catastrophic failure of the primary database,the standby database can be taken out of recovery mode and activated for on-line use. Once activated (opened), the standby database is then the primary database from the points of view of the customer's business and Oracle software.
The standby database is not intended for any other use other than as a disaster recovery database for the primary database. The standby database can not be queried or opened for any other purpose other than to activate in the event of catastrophic error of the primary database. Once the standby database is activated it can not be returned to standby recovery mode without recreating it again as a standby database, and the primary database will not have any transactional history beyond the point in time when the disaster occurred.
Click Here for information on temporarily switching to the standby and back to the primary database.
The following activities must be done by the database administrator to use the standby database feature:
The primary goal of these administrative procedures is to keep the control file, log files and data files consistent with each other as well as consistent between the primary and standby databases.