Disk allocation methods for Cartesian product files using unequal error protection codes

Allocation methods for Cartesian product files on multiple disks using linear error-correcting codes are discussed. In this paper, we propose an allocation method using unequal error protection (UEP) codes. Codewords of an UEP code have some special bits which are protected against a greater number of errors than the other bits. We firstly assume a model that “*”, which means “don´t care”, appears with different probability in each attribute of queries. In this case, the average access time can be calculated using the split distance distribution. Finally, we illustrate the average access time of the methods using UEP codes.