One of the largest U.S. processors of credit card transactions provides transaction authorization and settlement services for thousands of attached devices using a home-grown application on a pair of HPE NonStop systems. The processor recently upgraded its servers and implemented an HPE Shadowbase Disaster Recovery architecture (Figure 1).
The processor wanted to add additional servers and distribute them around the U.S. for disaster tolerance while efficiently utilizing these servers’ capacity. Additionally, fraudulent transaction activity was increasing and costing the processor a great deal of money. The processor needed to integrate real-time fraud detection into its transaction authorization services to identify suspicious activity. Directly modifying the authorization application processing would involve extensive and complex changes and require a lengthy testing cycle.
Since the databases are kept synchronized via asynchronous replication, data collisions can occur. As a request is received, it is applied and the application updates the record’s “update-timestamp” field, and then the change is asynchronously replicated to the other node so that all copies of the database are kept up-to-date. When data collisions occur (due to the nature of asynchronous replication), they are automatically resolved by a predetermined algorithm, which looks at a request’s record contents and applies the request with the most recent update timestamp (the other change loses and is logged to a reject log for record).
Note: Shadowbase supports other data collision resolution algorithms such as choosing the highest or lowest value of a specified field, or choosing the earlier update, depending on the underlying application’s need.
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