Oracle Data Guard 11g Handbook

Oracle Data Guard provides the best data protection and data availability solution for mission-critical databases that are the life-blood of businesses large and small. As bold as this statement is, Data Guard’s rich capabilities did not materialize overnight; Data Guard is a product of more than 15 years of continuous development. We can trace the roots of today’s Data Guard as far back as Oracle7 in the early 1990s. Media recovery was used to apply archived redo logs to a remote standby database, but none of the automation that exists today was present in the product. Instead, user-written scripts used FTP to transmit and register archive logs at the standby database. The Oracle7 feature was appropriately referred to as “manual standby.” Oracle8i capabilities evolved into the “automatic standby” feature, with automated log shipping (using Oracle Net Services) and apply. User-written
scripts were still the order of the day to resynchronize primary and standby databases in case they lost connection with each other. Also in the Oracle8i timeframe, Oracle made available prepackaged scripts for a limited number of platforms that simplified switchover and failover operations. These scripts could be downloaded from the Oracle Technology.
Network and were called Data Guard, introducing the present-day brand for the first time. Oracle9i was the first formal release of the Data Guard product that we know today. Replacing the Oracle8i scripts, the new release delivered a comprehensive automated solution for disaster recovery fully integrated with the database kernel—including automated gap resolution and the concept of protection modes, allowing customers to configure Data Guard more easily to meet their recovery point and recovery time objectives. Oracle9i also significantly enhanced redo transport services, adding synchronous and asynchronous redo transport methods as an alternative to traditional log shipping. For the first time, Data Guard could provide zero data loss protection all by itself, without the use of remote-mirroring technologies.


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