Oracle Data Guard

Oracle Data Guard is the management, monitoring, and automation software infrastructure that creates, maintains, and monitors one or more standby databases to protect enterprise data from failures, disasters, errors, and corruptions.
Data Guard maintains these standby databases as synchronized copies of the production database. These standby databases can be located at remote disaster recovery sites thousands of miles away from the production data center, or they may be located in the same city, same campus, or even in the same building.
If the production database becomes unavailable because of a planned or an unplanned outage, Data Guard can switch any standby database to the production role, thus minimizing the downtime associated with the outage, and preventing any data loss.Data Guard 11g builds upon an already unique set of capabilities, and redefines what users can expect from a disaster recovery solution. It can address both High Availability and Disaster Recovery requirements, and is the ideal complement to Oracle Real Application Clusters (Oracle RAC). Data Guard has the requisite knowledge of the Oracle database to reliably protect a standby database from corruptions that attempt to propagate from a primary database. It enables all standby databases, both physical and logical, to be used for productive purposes while in standby role. Data Guard delivers:
Reliability– optimum data protection and availability. You always know the state of your standby database and it can very quickly (in seconds), assume the primary role.
Lower cost and complexity – Data Guard's mature capabilities and rich management interface are included features of Oracle Enterprise Edition.
Maximum return on investment – All standby databases can be utilized for production

purposes while in standby role. Idle resources are eliminated.
Data Guard can be used in combination with other Oracle High Availability (HA) solutions such as Real Application Clusters (RAC), Oracle Flashback , Oracle Recovery Manager (RMAN), and new database options for Oracle Database 11g that include Oracle Active Data Guard and Oracle Advanced Compression, to provide a high level of data protection, data availability, and resource utilization that is unprecedented in the industry.

Data Guard Benefits
1. Disaster recovery and high availability:Data Guard provides an efficient and comprehensive disaster recovery and high availability solution. Automatic failover and easy-to-manage switchover capabilities allow quick role reversals between primary and standby databases, minimizing the downtime of the primary database for planned and unplanned outages.
2.Complete data protection: A standby database also provides an effective safeguard against data corruptions and user errors. Storage level physical corruptions on the primary database do not propagate to the standby database. Similarly, logical corruptions or user errors that cause the primary database to be permanently damaged can be resolved. Finally, the redo data is validated at the time it is received at the standby database and further when applied to the standby database.
3.Efficient utilization of system resources: A physical standby database can be used for backups and read-only reporting, thereby reducing the primary database workload and saving valuable CPU and I/O cycles. A physical standby database can also be easily converted back and forth between being a physical standby database and an open read/write database, without compromising data protection. A logical standby database enables read-write access to a synchronized standby database, and/or adding local tables to the standby database that can also be updated, and/or creating additional indexes to optimize read performance.
4.Flexibility in data protection to balance availability against performance requirements :Oracle Data Guard offers the maximum protection, maximum availability, and maximum performance modes to help enterprises balance data availability against system performance requirements.
5.Protection from communication failures :If network connectivity is lost between the primary and one or more standby databases, redo data cannot be sent from the primary to those standby databases. Once connectivity is re-established, the missing redo data is automatically detected by Data Guard and the necessary archive logs are automatically transmitted to the standby databases. The standby databases are resynchronized with the primary database, with no manual intervention by the administrator.
6.Centralized and simple management :Data Guard Broker automates the management and monitoring tasks across the multiple databases in a Data Guard configuration. Administrators may use either Oracle Enterprise Manager or the Broker’s own specialized command-line interface (DGMGRL) to take advantage of this integrated management framework.
7.Integrated with Oracle database Data Guard is available as an integrated feature of the Oracle Database (Enterprise Edition) at no extra cost.