Jupiter Station Diagnostic Program Alpha-11 was a diagnostic computer program with a holographic interface, a recreation of Doctor Lewis Zimmerman, in a recreation of the Jupiter Station Holoprogramming Center. It was a self-aware, learning hologram. In many ways it was similar to the EMH Mark I and was actually an adjunct program whose purpose was to act as a diagnostic tool in case the EMH developed faults.
When The Doctor began suffering memory problems, due to a cascade failure, B'Elanna Torres and Kes required the diagnostic program's assistance in finding a solution without completely wiping the Doctor's memory of the previous two years. Kes eventually discovered a solution, by "grafting" the EMH diagnostic program onto the damaged EMH, after which the diagnostic program itself would no longer exist (VOY: "The Swarm")