Oracle Distributed Systems

Chapter 12. Multi-Master Replication

Multi-master replication, also known as advanced replication orsymmetric replication, allows you to maintain multiple sets of identical data at various sites; Oracle can automatically synchronize all DDL and DML changes. Obviously, this functionality comes at the expense of additional planning and administrative tasks and introduces a new level of sophistication to the environment. This chapter describes how to create and maintain a replicated environment and how to assess its health.

Concepts and Terminology

As you embark down the road ofreplication, you will encounter several phrases repeatedly; these include:

• Deferred transaction

• Replication group

• Quiescence

• Master definition site

• Master site

• Replication support

• Conflict

• Propagation latency

• Instantiation

The following sections briefly describe what these phrases mean.

Deferred Transaction

A deferred transaction is a transaction that is queued for delivery to one or more remote databases. If you use multi-master replication with asynchronous propagation, Oracle creates deferred transactions for all local DML activity against the replicated tables.

Replication Group

A replication groupis a collection of one or more replicated objects (typically tables) that are administrated together. Very generally speaking, the objects in a given replication group are logically related; for example, they are often the set of objects that a given application uses. Prior to Oracle Version 7.3, the concept of a replication ...