Given a set of n data records with Li, data length and Pi, access frequency of data record Ri (1in), each data record is allocated in one of buckets, whose size is L, minimizing the access delay D, DPiPjdij dij: distance from allocated data record Ri to Rj, while satisfying the constraint that the size of data records in each bucket does not exceed L. The property of optimal allocation is investigated and an allocation heuristic is given whose slight modification gives the optimal allocation for the data records of up to 2 unit data length.