假設 M = 2 及 N = 3 的資料庫裡的資料項 X 之初值為 80，考慮以下排程（schedule）： T1: read_item(X); X:= X-N; T2: read_item(X); X:= X+M; T1: write_item(X); read_item(Y); T2: write_item(X); T1: Y:= Y-N; write_item(Y);