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Synchronizing Schema Changes and Managing Referential Integrity Violations

As a research and development company that is continually modifying its data collection and analysis techniques, Simbex faced several database synchronization challenges as the software continued to change and evolve after its deployment into customer environments. In this article, I discuss two of those challenges:

  • Central control over schema changes that must be pushed out to remote databases.
  • Central diagnosis of referential integrity violations that may occur on those remote databases.

Several features of the SQL Anywhere database and MobiLink synchronization software were used to solve these challenges, including:

  • " sp_hook" stored procedures for customizing the synchronization process.
  • The xp_read_file function for loading files into blob columns.
  • The EXCEPTION clause to perform try-catch error handling of SQL statements.
  • The STRING function for the dynamic construction of SQL statements to be run via EXECUTE IMMEDIATE.
  • The LIST aggregate function for constructing strings out of result sets.

The Simbex HIT System

On April 28, 2002, at a NASCAR race in Fontana California, Dale Earnhardt Jr. hit a concrete wall at 130 miles per hour. If he had been wearing a Simbex-equipped helmet, Earnhardt might not have been able to hide the severity of the head injury he received that day. Instead, Earnhardt suffered in secrecy and he did not reveal the full extent of his injury until several months later.

Simbex is a New Hampshire-based research and development company specializing in biomechanical feedback systems. Their premier product is the Head Impact Telemetry System, a real-time hardware and software system designed to measure and record blows to the head. Initially developed for use in college and high-school football, the HIT System lets sideline staff monitor the impact history for all players simultaneously, as well as providing pager alerts whenever a player receives a serious impact or series of impacts.

Impacts are measured by accelerometers in each helmet, visible as the small round knobs in Figure 1.

Figure 1: HIT System hardware mounted in a football helmet.

This data is sent wirelessly to the HIT System sideline controller in Figure 2.

Figure 2: HIT System sideline controller at a Virginia Tech football game.

A laptop computer is used to store, analyze and display the data locally; Figure 3 shows one of the displays where the impact history for one player is represented graphically.

Figure 3: HIT Impact Analysis screen display.

The HIT System sideline computer stores the impact data in a SQL Anywhere relational database system from Sybase's iAnywhere. As well as being analyzed and displayed out on the field, the data is also uploaded to a central SQL Anywhere database at Simbex headquarters for further analysis and study. The upload is handled by the MobiLink synchronization software that ships with SQL Anywhere, and I am proud to say I played a small role in the development of the HIT System by providing the MobiLink synchronization setup.

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