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ArcIMS Scalability Supports Heavy Demand for Site

Prior to its launch on September 6, 2002, the Los Angeles County Sex Offender Locator ( received extensive media coverage, which may have contributed to the initial flood of visitors to the site. Within the first 12 hours, the site received 2.4 million visitors—nearly four times the anticipated traffic. The site was a product of a collaboration by the Los Angeles County Chief Information Office (CIO), the Chief Administrative Office (CAO), Internal Services Department (ISD), and bp Spatial (formerly GIS/Trans Ltd.), an Esri business partner.

The application employs ArcIMS, ArcSDE, and ArcGIS. The tremendous volume of traffic meant some visitors initially experienced lengthy waits. However, because ArcIMS is a scalable, multithreaded system, additional servers were easily added without affecting the functionality of the software. Los Angeles County had contracted with Esri Professional Services prior to implementing the site, and the CIO, which provided project management, contacted for assistance in server balancing and optimizing the code.

Esri's Professional Services Division assisted in scaling the system to meet the demand, and within a day after the launch of the site most of those problems had been solved.

The application lets viewers create maps showing the number of sex offenders located within a specified radius of an address. Users can map offenders in relation to schools, parks, and libraries.

The CIO is also using the locator application as a model for developing a central resource and data repository for the county. "Instead of having duplicated databases and applications throughout the county, we can centralize them using single application engines. It's no longer cost effective for each department to redundantly maintain databases and applications," said John McIntire, associate chief information officer.

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