Data Synchronization

This section of the chapter excerpt tackles synchronizing data in the data hub.

As data content changes, a sophisticated and efficient synchronization activity between the "master" and the "slaves" has to take place on a periodic or an ongoing basis depending on the business requirements. Where the Data Hub is the master, the synchronization flows have to originate from the Hub toward other systems. Complexity grows if an existing application or a data store acts as a master for certain attributes that are also stored in the Data Hub. In this case, every time one of these data attributes changes in the existing system, this change has to be delivered to the Data Hub for synchronization. One good synchronization design principle is to implement one or many unidirectional synchronization flows as opposed to a more complex bidirectional synchronization. In either approach, the synchronization process may require transactional conflict-resolution mechanisms, compensating transaction design, and other synchronization and reconciliation functionality.

A variety of reasons drive the complexity of data synchronization across multiple distributed systems. In the context of a CDI Data Hub, synchronization becomes difficult to manage when the entire data environment that includes Data Hub and the legacy systems is in a peer-to-peer relationship. This is not a CDI-specific issue; however, if it exists, it may defeat the entire purpose and benefits of building a CDI platform. In this case, there is no clear master role assigned to a Data Hub or other systems for some or all data attributes, and thus changes to some "shared" data attributes may occur simultaneously but on different systems and applications. Synchronizing these changes may involve complex business-rules-driven reconciliation logic. For example, consider a typical non-key attribute such as telephone number. Let's assume that this attribute resides in the legacy Customer Information File (CIF), a customer service center (CRM) system, and also in the Data Hub, where it is used for matching and linking of records. An example of a difficult scenario would be as follows:

  • A customer changes his/her phone number and makes a record of this change via an online self-service channel that updates CIF. At the same time, the customer contacts a service center and tells a customer service representative (CSR) about the change. The CSR uses the CRM application to make the change in the customer profile and contact records but mistypes the number. As the result, the CIF and the CRM systems now contain different information, and both systems are sending their changes to each other and to the Data Hub for the required record update.
  • If the Data Hub received two changes simultaneously, it will have to decide which information is correct or should take precedence before the changes are applied to the Hub record.
  • If the changes arrive one after another over some time interval, the Data Hub needs to decide if the first change should override the second, or vice versa. This is not a simple "first-in first-serve" system since the changes can arrive into the Data Hub after the internal CIF and CRM processing is completed, and their timing does not have to coincide with the time when the change transaction was originally applied.
  • Of course, you can extend this scenario by imagining a new application that accesses the Data Hub and can make changes directly to it. Then all systems participating in this change transaction are facing the challenge of receiving two change records and deciding which one to apply if any.

This situation is not just possible but also quite probable, especially when you consider that the Data Hub has to be integrated into an existing large enterprise data and application environment. Of course, should the organization implement a comprehensive data governance strategy and agree to recognize and respect data owners and data stewards, it will be in a position to decide on a single ownership for each data attribute under management. Unfortunately, not every organization is successful in implementing these data management structures. Therefore, we should consider defining conceptual Data Hub components that can perform data synchronization and reconciliation services in accordance with a set of business rules enforced by a business rules engine (BRE).


Data Management Concerns of MDM-CDI Architecture
  Introduction
  Data Strategy
  Data Quality
  Managing Data in the Data Hub
  Data Synchronization
  Overview of Business Rules Engines
  Metadata Basics
This was last published in June 2008

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