Comments on “Process synchronizaiton in databases systems”

r<[U] means “process i reads variable u”; wi[u] means “process i writes into variable v.” Sequences of r’ s and w’ s denote schedules. Process Pi” initializes the database state and PO,, reads the final database state. PI, Pz, and Pa are user processes. Theorem 3.1 states that a schedule is serializable only if whenever two processes have conflicting actions, ail pairs of conflicting actions appear in the same order. (Two actions conflict if they operate on the same variable and one of them is a write action.) Consider schedule S: