Thomas Write Rule

In computer science, particularly the field of databases, the Thomas Write rule is a rule in timestamp-based concurrency control.

It states that, if a more recent transaction has already written the value of an object, then a less recent transaction does not need perform its own write since it will eventually be overwritten by the more recent one.

For example:

\begin{bmatrix}
T_1 & T_2 \\
& Read(A) \\
Read(B) & \\ &Write(C) \\
Write(C) & \\
Commit & \\
& Commit \end{bmatrix} \Longleftrightarrow
\begin{bmatrix}
T_1 & T_2 \\
& Read(A) \\
Read(B) & \\
& Write(C) \\ & \\
Commit & \\
& Commit\\
\end{bmatrix}

Assuming that the timestamp of T1 is less than that of T2, T1's write is discarded.

If TS(T)Thomas Write Rule

Famous quotes containing the words write and/or rule:

    I read, with a kind of hopeless envy, histories and legends of people of our craft who “do not write for money.” It must be a pleasant experience to be able to cultivate so delicate a class of motives for the privilege of doing one’s best to express one’s thoughts to people who care for them. Personally, I have yet to breathe the ether of such a transcendent sphere. I am proud to say that I have always been a working woman, and always had to be ...
    Elizabeth Stuart Phelps (1844–1911)

    Resolved to ruin or to rule the state.
    John Dryden (1631–1700)