A method is proposed for quantitatively evaluating the availability of a distributed transaction system (DTS). The DTS dynamicscan be modeled as a Markov process. The problem of formulatingthe set of linear homogeneous equations is considered, obtaining the related coefficient matrix, that is, the transition rate matrices of the DTS elements. Such operations can be performed according to the rules of Kronecker algebra. The transition rate matrices are used to calculatethe probabilities of the different possible states of the DTS. The availability with respect to a transaction T is computed through its representation by means of a structure graph and a structure vector related to the probabilistic state of the DTS element relevant to the transaction T itself. Copyright © 1985 by The Institute of Electrical and Electronics Engineers, Inc.