A holographic lab, or hololab, was a facility were holograms would go for maintenance.
In 2378, a Federation mining facility had a hololab for maintenance of repurposed EMH-Mark I holograms. Often, holograms informed one another to report to the hololab for maintenance. In one instance of this, one hologram suggested to another that it ask the operator to run file 47-Beta, which contained a copy of the holonovel Photons Be Free.
Chapter 6, "Duel in the Ready Room" of Photons Be Free had Captain Jenkins order Tulak and Kymble to escort the protagonist to the hololab aboard the USS Vortex for reprogramming. (VOY: "Author, Author")