A tactical database is a system of computer files containing information relevant to combat maneuvers, armaments, and the relative strength of offensive and defensive technologies. Most starships carried a tactical database, with which to access information pertaining to shields and weapons.
In 2371, Kes's counterpart from five years in the future used her psionic abilities to circumvent the command authorization necessary to access the USS Voyager's tactical database. Kes subsequently transmitted the information to an attacking Vidiian vessel, in her misguided attempt to change history and return herself to Ocampa. (VOY: "Fury")
In 2373, Harry Kim, Voyager's operations officer, downloaded a Borg tactical database from a distribution node on board a wrecked Borg cube. Analyzing the information, the crew learned about the conflict between the Collective and Species 8472. (VOY: "Scorpion")
In 2376, the Voyager crew encountered the Ba'neth, an extremely reclusive Delta Quadrant species, while one of them attempted to covertly download Voyager's tactical database from the Delta Flyer. (VOY: "Riddles")
As part of The Doctor's upgrade to the Emergency Command Hologram, he was installed with a tactical database containing information and tactics from some of history's notable battles. One such conflict was the Battle of Vorkado, wherein a Romulan captain created a photonic shockwave to disable two pursuing enemy vessels. In 2377, The Doctor recreated the maneuver to disable two Quarren patrol ships. (VOY: "Workforce, Part II")