UNIVERSITY OF SOUTHAMPTON FACULTY OF ENGINEERING , SCIENCE AND MATHEMATICS School of Electronics and Computer Science Rigorous Design of Distributed Transactions by Divakar Singh Yadav

Transaction States In our model of transactions, an update transaction, once started, updates the abstract database atomically when the transaction commits, or makes no changes in the database, when it aborts. We have represented the global state of update transactions by a variable transstatus in the abstract model of the transactions. The variable transtatus is defined as transtatus ∈ trans → TRANSSTATUS, where TRANSSTATUS={COMMIT,ABORT,PENDING}. The transstatus maps each transaction to its global state. With respect to an update transaction, activation of the following events change the global transaction states. Chapter 7 Liveness Properties and Modelling Guidelines 129 – StartTran(tt) : The activation of this event starts a fresh transaction and the state of the transaction is set to pending. – CommitWriteTran(tt) : A pending update transaction commits by atomically updating the abstract database and it status is set to commit. – AbortWriteTran(tt) : A pending update transaction aborts by making no change in the abstract database and its status is set to abort.