When Esri released ArcIMS back in 2000, which was solely designed with one purpose in mind, to share maps over the Internet, they never anticipated that it would take off. The web was at its boom, but people were still reluctant to move from their comfort desktop zone to web browsers. Smart phones hadn't tipped yet, so there was no need for mobility and portability with the GIS data. Despite all that, ArcIMS did spread, and it became one of the most used software for sharing maps. The problem with ArcIMS was that it wasn't designed to run on a distributed environment. Changing the architecture of the product was indeed expensive, especially with all these users having stabled their customizations around this technology. The President of Esri has always been fascinated with the concept of cloud computing and sharing maps over thin clients. Therefore, Esri decided to start a new project. The project was named ArcGIS Server.
ArcGIS Server was designed to scale on multiple machines and was equipped with a load-balancing module to balance the requests between the different machines. Not only you could author, publish, and share maps on Server, but it was also equipped with a new feature, geoprocessing, which made it replace ArcIMS altogether. Users can now run tasks on their data to be processed and returned, and they can even combine different tasks into models and create more complex geoprocessing models. Recently, Esri changed the name of ArcGIS Server to ArcGIS for Server for marketing purposes. Ten years after its release, Esri ceases the support of ArcIMS and refocuses its resources on ArcGIS for Server.
