Timestamp-based concurrency control

In computer science, a timestamp-based concurrency control algorithm is a non-lock concurrency control method. It is used in some databases to safely handle transactions, using timestamps.

A number of different ways have been used to generate timestamp

Each transaction (${\displaystyle T_{i}}$) is an ordered list of actions (${\displaystyle A_{ix}}$). Before the transaction performs its first action (${\displaystyle A_{i1}}$), it is marked with the current timestamp, or any other strictly totally ordered sequence: ${\displaystyle TS(T_{i})=NOW()}$. Every transaction is also given an initially empty set of transactions upon which it depends, ${\displaystyle DEP(T_{i})=[]}$, and an initially empty set of old objects which it updated, ${\displaystyle OLD(T_{i})=[]}$.

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