Ingres® 2006 - Replicator Option User Guide

Peter Kitson

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Chapter 2: Understanding the Replicator Option


This chapter introduces Ingres Replicator Option and describes its benefits. It covers the following topics:

  •   Introduction to Ingres Replicator Option
  •   Product requirements
  •   Ingres Replicator Option terminology
  •   Ingres Replicator Option components
  •   Ingres Replicator Option design concepts
  •   Sample configurations
  •   Role of the distributed database administrator

Replication

Replication is the act of maintaining identical copies of a defined set of data in more than one database. Replication allows continuous access to your databases, protects against catastrophic failures, improves performance, and is an excellent means of maintaining data across different database systems.

Ingres Replicator Option

Ingres Replicator Option is a database connectivity system that manages replication. It provides transparent replication of data across databases on local or remote sites.

You can replicate between different databases on the same machine or on different machines on the other side of the world, as long as they are in a distributed network. So instead of having all your users throughout the world access the same database in one location, you can have a replicated database in every region.

Data from a transaction are not available for replication until the transaction has committed locally.

Ingres Replicator Option works behind the scenes to replicate data asynchronously by transaction. Designed as a layer that sits between the database and an application, Ingres Replicator Option is transparent to users. Ingres Replicator Option queues each replicated transaction and uses twophase commit to move the transaction from the Ingres Replicator Option queues to the target database. In the event of a source, target, or network failure, data integrity is enforced through this two-phase commit protocol by ensuring that either the whole transaction is replicated, or none of it is.
 
If the replication fails during two-phase commit, it remains in the queue and is tried again. Therefore, if one replicated database goes down, all the transactions that must be replicated to it remain queued and is sent again in the correct order as soon as it becomes available. For more information, see How Two-Phase Commit Works (see page 28).

Note: Two-phase commit is not available for installations running the Ingres Cluster Solution. For information on how to turn off two-phase commit and use Ingres Replicator Option with clusters, see the appendix “Cluster Support.”

Ingres Replicator Option also allows you to monitor your replicated transactions and run reports on your replication system.