Storage-base replication solutions technologies are based upon the storage-array based replication of data. Thus, the source of data does not matter. All kinds of application and database data can be replicated to a remote location, where Data Guard is only able to replicate Oracle databases.

In general there are two kinds of storage-based replication: synchronous and asynchronous replication. Synchronous replication means that each update to the source storage unit must also be updated in the target storage unit before another update can process. This guarantees zero data loss in the case of primary site failure. However, synchronous replication affects the I/O respond performance of the primary system depending on the distance between sites and network capacity. Therefore, this technology is distance limited. Synchronous replication technologies support up to 300 km distance between sites in the current technology level.

Asynchronous replication provides a long-distance replication solution with minimal impact on performance. In some products, the main problem with the asynchronous mode is the data consistency on the secondary site. The primary site sends a periodic, incremental copy of updates to the secondary site instead of a constant stream of updates. So there is no guarantee that dependent write operations on the primary site are transferred and applied to the remote destination in the same sequence.

Using storage-based replication solutions, it's not possible to start an Oracle instance and query database on the secondary site using the disks with the replicated data because of the data inconsistency issue. However Data Guard offers Active Data Guard, which enables users to query the standby database while replication is on the go. Some other advantages of Data Guard over storage-based replication solutions are enhanced corruption detection and prevention, automated database failover (fast-start failover), and RMAN backup offloading features that may not benefit from the use of storage-based replication solutions.

GoldenGate is a data replication and integration tool for heterogeneous environments. It provides real-time capture, transformation, routing, and delivery of database transactions across heterogeneous systems (Oracle, DB2, MySQL, SQL Server, Sybase, Teradata, Netezza, and so on). Oracle agreed to acquire GoldenGate software in 2009 and then released 10.4, 11.1, and 11.2 versions with new enhancements. On the other hand, Streams is a built-in feature of the Oracle database that was first announced with database Version 9.2 and allows information sharing within an Oracle database or between Oracle databases.

Their common property is their capability of capturing, propagating, and applying data changes between Oracle databases.

On the other hand their main differences are:

Because of the GoldenGate's wider technology infrastructure and flexibility over Streams, Oracle announced that Oracle Streams will continue to be supported, but will not be actively enhanced and the best elements of Oracle Streams will be evaluated for inclusion with Oracle GoldenGate. It was also indicated that GoldenGate is the strategic product of Oracle on data distribution and data integration.

An important feature of GoldenGate that makes the product different from its counterparts is the bidirectional replication capability, which is also called active-active replication. With this feature the primary and standby concepts are replaced by two active primary sites. Updates on site A are replicated to site B, and updates on site B are replicated to site A. The main challenges here are conflict handling and loop detection. A conflict is likely to occur in a bi-directional environment, where the same row or field is being updated at both sides and the changes are replicated. In this situation, a decision needs to be made if both transactions fail, or one transaction overwrites the other. The other key point is loop detection. If an update is replicated from site A to site B and then the same update from site B to site A, and so on, this loop needs to be detected and solved. The following diagram shows the general structure of an active-active GoldenGate configuration:

GoldenGate is a preferred solution to extract data from production databases in order to feed the data warehouse. It offers much flexibility to select specific data on the database and if needed transform the data before it hits the target.

The replication market's leaders, namely, Data Guard, storage-based replication products, and GoldenGate are compared in the following table with their most important features. Streams is out of this comparison because of the strategy mentioned by Oracle on its replication products:

After reviewing the comparison table, it's obvious that Data Guard has better properties for high availability and disaster recovery purposed Oracle database replication. Storage-based replication products offer disaster recovery solution for the complete IT infrastructure data; however, when the case is Oracle databases, they cannot offer the Oracle integrated, flexible, and automatized features as in Data Guard. On the other side, we can see that GoldenGate was positioned especially for ETL and data integration requirements and it has great flexibility in this field. However, it also cannot reach Data Guard standards on data protection and disaster recovery.