Shulou(Shulou.com)06/01 Report--

Oracle ADG vs DG

In fact, he had already done ADG's experiment, but he did not know that it was an upgraded version of DG.

ADG: Active Data Guard

DG: Data Guard

What is the difference between DG and ADG ?

From the docs:

Oracle Data Guard ensures high availability, dataprotection, and disaster recovery for enterprise data. Oracle Data Guardprovides a comprehensive set of services that create, maintain, manage, andmonitor one or more standby databases to enable production Oracle databases tosurvive disasters and data corruptions. Oracle Data Guard maintains thesestandby databases as copies of the production database. Then, if the productiondatabase becomes unavailable because of a planned or an unplanned outage, OracleData Guard can switch any standby database to the production role, minimizingthe downtime associated with the outage. Oracle Data Guard can be used withtraditional backup, restoration, and cluster techniques to provide a high levelof data protection and data availability.

Oracle DG guarantees high availability, data protection, disaster recovery for enterprise data. Oracle DG provides a comprehensive set of services, such as the creation, maintenance, management and monitoring of one or more backup repositories, enabling production repositories to recover from disasters and data crashes. Oracle DG maintains these backup libraries as copies of production libraries. In the event of a planned or unplanned outage of the production depot, DG can switch the role of any backup depot to that of the production depot to minimize downtime due to the outage. DG can also be used as a traditional clustering technology for backup, recovery, and data high availability and protection.

So both DG and ADG provide those additional copiesof the database. Early DG versions provided that facility solely for disasterrecovery. Nowadays, there are many other things you can use DG for, eg, youcould backup the DG copy rather than the production database to ease resourceconsumption etc.

Both DG and ADG therefore provide additional copies of the database. Earlier versions of DG only provided disaster recovery of data. Now you have a lot of other things you can use with DG, such as you can backup DG libraries instead of production libraries to reduce resource consumption.

Where ADG offers more is that you can have thedatabase open for read-only (eg reports) whilst it is still being kept in syncwith your primary database. With normal DG, if you want it open read-only, youmust pause the sync process.

What ADG offers is that you can have DG libraries open in read-only mode while DG libraries remain synchronized with the master library. For regular DG, you open DG libraries as read-only and must pause the synchronization process.

What is the difference betweenADG and GoldenGate ?

ADG maintains a physical copy of yourprimary database (that can be read by queries). You are100% positive that it and the primary are the same.

Goldengate replicates *changes* from yourprimary database to a secondary but quite separate copy of your database. This second copy might be a subset, or superset, or simply bedivergent from your primary. The advantage is that this secondarydatabase can be read-write... its really a *different* database into whichchanges are being pushed.

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