Oracle Tips  by Burleson Consulting

The Data Warehouse Development Life Cycle

Distributed Oracle Data Warehouses Replication And Referential Integrity

If a distributed Oracle database uses table replication such that the business rules span physical databases, then we need to address the maintenance of referential integrity (RI). When replicated tables are implemented with RI, a problem sometimes occurs when periodic updates to replicated tables cause a situation where some business rules are violated. For example, consider the simple business rule that no customers may be deleted if they still have outstanding orders in the order table. While this rule can be maintained easily in the master database, what happens when the dependent tables are replicated? (See Figure 9.8.) If a local task on a slave database deletes a row for a customer named Smith, it may do so without the knowledge that orders exist on the master database for customer Smith.

Figure 9.8 Replication and referential integrity.

There are two methods that an Oracle developer can use to solve the problem of maintaining referential integrity while using table replication. The first method is to run a query against the master order table to see if rows exist for a particular customer. The second solution is to feed the slave task back to the master database so Oracle can detect RI violations.

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