Before fetching cell data, the application has to create an accessor that describes the structure of the data buffer. This is done using IAccessor::CreateAccessor method. The accessor created using this method is given as an input parameter to the IMDDataset::GetCellData method. Since GetCellData can fetch multiple cells in a single call, the provider needs to know the size of each cell in the data buffer. Applications must provide this size in the cbRowSize argument of IAccessor::CreateAccessor method. Failure to do so will result in an error from this method and an accessor will not be created.