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Optimistic Concurrency Control (OCC)

Learn how optimistic concurrency control manages concurrent transactions without locking by using timestamps and local copies. Explore its three phases: start, read and modify, and validation. Understand how validation ensures isolation with techniques such as version checking and timestamp ordering to maintain data consistency.

Optimistic concurrency control (OCC) is a concurrency control method that was first proposed in 1981 by Kung et al.H. T. Kung and J. T. Robinson, “On optimistic methods for concurrency control,” ACM Transactions on Database Systems, Volume 6, Issue 2, 1981., where transactions can access data items without acquiring locks on them.

In this method, transactions execute in the following three phases:

  • Begin
  • Read & modify
  • Validate & commit/rollback

Begin phase

In this phase, transactions are assigned a unique ...