Multi-master replication

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Multi-master replication is a method of replication employed by databases to transfer data or changes to data across multiple computers within a group. Multi-master replication can be contrasted with a master-slave method (also known as single-master replication). Benefits of Multi-master replication :

If one master (e.g. Microsoft's domain controller) fails, other masters will continue to update the database.

Masters can be located in several physical sites i.e. distributed across the network.

Disadvantages of Multi-master replication :

Database is loosely consistent.

1 Implementations
- 1.1 Active Directory
- 1.2 Oracle
2 See also
3 References

[edit] Implementations

[edit] Active Directory

One of the more prevalent of multi-master replication implementations is Microsoft's Active Directory. Within Active Directory, objects that are updated on one Domain Controller are then replicated to other domain controllers through multi-master replication. It is not required for all domain controllers to replicate with each other's domain controller as this would cause excessive network traffic in large Active Directory implementations. Instead, domain controllers have a complex update pattern that ensures that all servers are updated in a timely fashion without excessive replication traffic. Some Active Directory needs are better served by Flexible single master operation.

[edit] Oracle

Oracle database clusters implement multi-master replication using one of two methods. Asynchronous multi-master replication commits data changes to a deferred transaction queue which is periodically processed on all databases in the cluster. Synchronous multi-master replication uses Oracle's two phase commit functionality to ensure that all databases with the cluster have a consistent dataset.