When you don't have time for the usual synchronization process
Suppose you're a DBA using SQL Server 7.0 to support online transaction processing (OLTP) databases of 50GB or more in a virtually 24 * 7 operation with a narrow maintenance window. Suppose also that your users require ad hoc query access to your data for either reporting purposes or data warehouse development. For this example, you would want to maintain a copy of the production data on a separate server to avoid database performance problems such as blocking caused by users issuing long-running queries against tables that programs are also issuing inserts and updates on.
Tra...