The issue of priority assignment is addressed, in firm multiclass real-time database systems (RTDBSs) where classes are distinguished by their mean sizes. It is shown that the earliest deadline scheduling principle, upon which a number of existing priority assignment policies are based, discriminates significantly against longer transactions. This observation has motivated the development of a novel dynamic priority assignment scheme that improves the chances for long transactions to meet their time constraints, thereby providing a fairer mechanism for use in multiclass RTDBS transaction scheduling.