One of the situations that we encountered was related to how tracking occurs. We have one department that wanted to use the single-entry-mode, but most other departments did not want to use that level of tracking and instead wanted to use percent complete.
Project Server’s Single-Entry-Mode feature is an on/off feature, so in order to accomodate this we had to set up a separate PWA for those departments using this feature as their tracking method for projects.
