Editing Optimistic concurrency control (section)

== Phases of optimistic concurrency control ==
Optimistic concurrency control transactions involve these phases:<ref name="KungRobinson1981" />
*'''Begin''': Record a timestamp marking the transaction's beginning.
*'''Modify''': Read database values, and tentatively write changes.
*'''Validate''': Check whether other transactions have modified data that this transaction has used (read or written). This includes transactions that completed after this transaction's start time, and optionally, transactions that are still active at validation time.
*'''Commit/Rollback''': If there is no conflict, make all changes take effect. If there is a conflict, resolve it, typically by aborting the transaction, although other resolution schemes are possible.  Care must be taken to avoid a [[time-of-check to time-of-use]] bug, particularly if this phase and the previous one are not performed as a single [[linearizability|atomic]] operation.