Two first-year sitcoms have been picked up for additional episodes, with CBS giving a full-season commitment to TriStar TV’s “The Nanny,” while NBC confirmed punching up additional episodes of its on-hiatus comedy “The Second Half.”“The Nanny,” which premiered Nov. 3 with an eight-episode order, has been upped to a full complement of 22 segments. With the two-week interruption of CBS’ regular primetime lineup in February for the Winter Olympics, that means the network could conceivably air new segments of the Fran Drescher vehicle straight through the May sweeps. CBS recently flopped the show with its 8-9 p.m. Wednesday running mate, the sophomore comedy “Hearts Afire,” having the TriStar show lead off the hour. “Nanny” has consistently built on “Hearts’ ” lead-in — averaging a 9.2 rating, 14 share in Nielsen for its Wednesday airings — during an hour where CBS has consistently struggled. The show performed better in a Monday airing Dec. 6, and the network will apparently try to give the sitcom another boost with a second stunt outing Jan. 24. “The Nanny” is the third member of CBS’ freshman class to receive a full-season order, joining the Monday sitcom “Dave’s World” and Thursday serial “Second Chances.”"Harts of the West” was also upped to 13 installments. “Second Half,” meanwhile, gets a four-episode extension, joining the two of its initial 13 that have yet to air. The Castle Rock show, starring comic John Mendoza, ran up little Nielsen yardage at 9:30 p.m. Tuesdays, where it followed “The John Larroquette Show.” Even staffers assumed the show was finished in November, but NBC decided to give “Second Half” a second chance. Castle Rock also supplies the Peacock web its top-rated series, “Seinfeld.” NBC has now ordered additional episodes of eight new series, including “seaQuest DSV,” which began the year with a 22-episode commitment.