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Chapter 7.  The Replicator

The Replicator provides the transactional replication from one grid to another, based on CloudTran transactions. Replication goes from the "local" Grid to a "remote" Grid.

The replicator is specifically for "system of record in the grid" applications that are concerned with preserving transactional consistency at a remote grid.

  • If the system of record is the database, it makes more sense to use a database-driven replication approach, like GoldenGate.
  • If you are not concerned about transactionality, using the standard Coherence replication is more appropriate.

The key characteristics of the replicator are:

  • "Replicate-behind". In other words, the replicator does not wait for an acknowledgement from the remote grid that a transaction has committed, before committing at the local grid. This avoids long transactional delays (of 100ms or more).
  • Replicator-specific transaction log, which *is* committed before the local transaction is committed. This adds a very small delay (less than the time for one network message on average, if SSD drives are used).
  • No single point of failure - dual drives can be used, and the replicator is provided as a service that fails over.
  • Active-Passive and Active-Active configurations supported. Previous values are sent along with changed values so double-update conflicts can be detected.
The replicator is an optional feature: it must be switched on to become active.

This chapter explains how the CloudTran Replicator functions and how to configure the various aspects of the Replicator.

7.1  Replicator Overview

7.2  Local Store

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