In computer science, in the field of databases, the Thomas Write rule is a rule in timestamp-based concurrency control.
Given a Timestamp on a transaction T, TS(T) and Write Timestamp on an object O, WTS(O):
It states if TS(T) < WTS(O), the current write action has been made obsolete by the most recent write of O, which follows the current write according to timestamp ordering.
Given a non-conflict serializable transaction schedule:
The Thomas Write Rule relies on the fact that T2's write on object A is never seen by any transaction and postulates that the schedule above is equivalent to the schedule below:
This schedule is the same as the first and is conflict serializable.
