By 2003, the City of Ocala had converted their two monitoring & control systems to VTScada software from Trihedral. In 2005, they merged the two into a single application.
In that system, servers at six remote sites logged sensor data to a central historical database at the main office. When operators at each site opened a trend window or ran a report, the data came from this database.
This common SCADA architecture poses two potentially serious issues; especially for utilities that rely on historical data to control costs. If the network goes offline, users at each site cannot access the historian. Also, data collected during the interruption is lost.
In April of 2011, Trihedral President, Glenn Wadden, and programmer, Will Dumaresq, traveled to Ocala to implement a new distributed approach to historical data that Trihedral developed specifically for large data-rich SCADA systems. In this article Wadden describes the challenges of transforming the database architecture without interrupting the process or losing data.