Table Replication Techniques Oracle Tips by Burleson Consulting

The Data Warehouse Development Life Cycle

Distributed Oracle Data Warehouses

Table Replication Techniques

One of the easiest ways to improve warehouse availability is with data replication. In order to bypass many of the problems inherent with network communications, data is copied and stored in multiple Oracle databases. Mainly, warehouses replicate information to improve reliability and maximize query response times. As you may know, in a client/server environment, it is often difficult to get all of the data to all of the users who require the information. It is also difficult to balance processing requirements between light data users (e.g., online transaction processing systems) and heavy data users (e.g., data warehouse systems for marketing). Data replication is often a desirable choice when processing requirements demand that online systems get fast response times while intensive I/O analysis is performed concurrently against the same information.

Another benefit of table replication is that if there is a failure with one of the component databases, the replicated database information remains available. This type of data replication is commonly called data distribution. Data distribution is not always the same thing as a distributed database. With data distribution, information can be redundantly copied to another database, whereas in “true” distributed databases the information is not replicated even though the data may reside in many databases. As mentioned earlier, some installations create master-slave replication, where a master database is used for updating multiple query, or slave, databases each day. The master-slave method usually has a "change" database that keeps track of all changes made to the master database. When the time comes to propagate the changes to the slave databases, a background task is triggered to copy the data, and the changed entries are then removed from the change database.

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This is an excerpt from "High Performance Data Warehousing", copyright 1997.

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