How to license Oracle’s Data Guard vs Active Data Guard?

Data Guard vs. Active Data Guard

The Data Guard feature provides a comprehensive set of services that create, maintain, manage, and monitor one or more standby databases to enable production Oracle databases to survive disasters and data corruptions. Data Guard maintains these standby databases as transactionally consistent copies of the production database. Data Guard is a feature of the Oracle Database Enterprise Edition itself and does not require separate licensing.

On the other hand, Active Data Guard is a so-called Oracle Database Enterprise Edition Option and as such requires separate licensing. Active Data Guard was introduced with Oracle Database 11g Release 1 to provide important extensions to basic Data Guard functionality that further enhance data protection, availability, and return on investment (ROI) in standby systems. To be concrete both the primary production server and the secondary DR server are required to be fully licensed and the same license metric should be applied as to the associated licenses for the Oracle Database itself.

Active Data Guard includes a number of features and functionalities, such us:

• Real-Time Query to offload read-only workloads to an up-to-date standby database. This adds capacity, improves response time, and increases return on investment. It also provides continuous validation that the standby database is production-ready.
• Automatic Block Repair to transparently repair physical corruptions wherever they occur, at either the primary or standby database.
• Far Sync to enable zero data loss protection and off-host network compression, even when primary and standby are hundreds or thousands of miles apart.
• RMAN Block Change Tracking to offload fast incremental backups to an Active Data Guard Standby with 20x the performance of traditional incremental backups.
• Active Data Guard Rolling Upgrade to make it simple to reduce planned downtime and minimize the risk of introducing changes to production systems.
• Global Database Services to provide intelligent load balancing and automated service management across replicated databases.
• Application Continuity to make outages transparent to users by reliably handling in-flight transactions.

Active Data Guard is an evolution of Data Guard technology that improves production database performance for critical transactions. As such, both Active Data Guard and Data Guard are related technologies, but their use results in different licensing requirements.

But what is Data Guard Observer?

Data Guard Observer is a component of the Oracle Data Guard command-line interface which monitors the availability of the primary database. The Observer continuously monitors the fast-start failover environment to ensure the primary database is available. You can achieve a reduction in downtime or zero downtime and maintain user connectivity to the primary system active by using Data Guard Observer. Installing and starting the Observer is an integral part of using fast-start failover.

In order to use fast-start failover (FSFO) you must install DGMGRL (Data Guard Broker Command Line Interface) and run the Observer software. So, fast-start failover is a feature of Oracle Data Guard and cannot run without a Data Guard Broker configuration. Only one Observer can be observing the broker configuration at any given time. You have to use the DGMGRL command to determine the location of the Observer that is currently associated with the broker configuration.

If the Observer’s host machine crashes, the broker configuration is no longer observed and fast-start failover is no longer possible. In this case, you may have to move the Observer to a new host if the original host machine cannot be repaired in a timely fashion. To move the Observer, you must stop allowing the first Observer to observe this broker configuration, and then start a new Observer.

Starting with Oracle 12cR2 it is possible to configure multiple Observers within a single Oracle Data Guard broker configuration. Multiple Observers provide an immediate benefit for High Availability. If one Observer fails, there are additional Observers that can continue to monitor the status of the configuration.

Do I require a license for the client itself?

As per Oracle’s program documentation, the Client software (to connect with the Oracle Database) can be installed separately on the specific end user device that connects to the Oracle Database. The installation of the Oracle Client itself as such does not require separate licensing, as long as the Oracle Database itself as installed on a server is licensed with sufficient Named User Plus and/or Processor licenses.