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2 Overview : 2.1 Why Use Replication
2.1 Why Use Replication
Replication of data can be employed in a variety of use cases in organizations where it is important to use the same data in multiple settings. This allows users to work with ‘real’ data that will yield ‘real’ results that are reliable in more than one setting. Support of both single-master and multi-master replication gives xDB Replication Server a broad range of supported use cases.
Some of the more popular uses of single-master replication include the following:
2.1.1 Offloading Reporting and Business Intelligence Queries
In this use case, users take all or just a subset of data from a production OLTP system and replicate it to another database whose sole purpose is to support reporting queries. This can have multiple benefits: a) reporting loads are removed from the OLTP system improving transaction processing performance, b) query performance improves as well without being subordinated to transactions on the system, and c) in Oracle installations, the reporting server duties can be handled by a product like Advanced Server reducing licensing costs for a reporting server.
2.1.2 Using Warm Standby Servers
When many organizations wish to improve the availability of their data, a cost effective solution is often the use of warm standby servers. These are database servers kept up to date with the online system through replication that can be brought online quickly in the event of a failure in the production system. Warm standby servers can also be used for regular maintenance by gracefully switching over to the standby server so that the production server can be brought offline for regular maintenance.
2.1.3 Testing Systems in Parallel
Often times, upgrading or moving to a new database system requires that the old and new systems be up and running in parallel to allow for testing and comparing results in real time. Replication can be employed in this use case and is frequently used in development and testing environments.
2.1.4 Migrating Data
Similar to running in parallel, is the situation where data may be migrated from one system to another in a sort of ‘seeding’ operation. Replication can be very effective in this situation by quickly copying data.
Some reasons to consider multi-master replication include the following:
2.1.5 Write Availability
In single-master replication, only the master database is available for writes. The slave databases are read-only for applications. If the replicated target databases must be available for write access as well, multi-master replication can be employed for the same use cases as outlined for single-master replication, but with the additional advantage of write access to the slaves.
2.1.6 Write Scalability
In write-intensive applications, multi-master replication allows you to utilize multiple database servers on separate hosts to process write transactions independently of each other on their own master databases. Changes can then be reconciled across master databases according to your chosen schedule.
2.1.7 Localized Data Access
In a geographically dispersed application, local access to the database can be provided to regions of clients. Having the database servers physically close to clients can reduce latency with the database. Multi-master replication allows you to employ a WAN connected network of master databases that can be geographically close to groups of clients, yet maintain data consistency across master databases.
2 Overview : 2.1 Why Use Replication

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