24-10-2014, 09:30 AM
Abstracts: The primary database is the production database, and the standby database is the remote, secondary database. Oracle Data Guard is an option to the Oracle RDBMS. It maintains a standby database as an alternative database to primary database. In the event of failure, the standby database can be activated and assume the primary database role. Oracle physical standby protects from user and logical errors by maintaining consistent copies of redo data of the primary database at the standby database. The Oracle physical standby database is kept synchronized with the primary database by using media recovery to apply redo data that was generated on the primary database (REDO APPLY). The Oracle logical standby database is kept synchronized with the primary database by using media recovery to apply redo data into SQL statements and then executing those SQL statements against the standby database (SQL APPLY).