Starfleet Operational Support Services

From Memory Alpha, the free Star Trek reference.

Starfleet Operational Support Services was an agency of Starfleet in the 2360s. This branch worked in conjunction with starbases and other Starfleet facilities. Their duties included routine maintenance of Starfleet starships, the upgrading of ships' computers, and the repairing of damaged ships.

Starbase 74, in the Tarsas system, worked with this agency in performing routine maintenance and computer upgrades on the USS Enterprise and in repairing the USS Melbourne in 2364. (TNG: "11001001")

The branches of Starfleet
Earth Starfleet: Command • Materiel Supply Command • Medical • Mission Control • Security • Section 31 • Training Command
Federation Starfleet: Administration • Administrative Operations • Advanced Technologies • Command • Communications • Control • Dental • Engineering Corps • Exploratory Division • Information • Inspector General • Intelligence • Internal Affairs • Judge Advocate General • Materiel Supply Command • Medical • Mission Operations • Operational Support Services • Operations • Orbital Operations • OSHC • Research and Development • Science • Section 31 • Security • Shipyards Operations • Stellar Imaging • Tactical • Training Command • Warp Technologies