# Vector Clocks

> A mechanism that keeps one counter per node on each update, so two updates can be compared as ordered or concurrent.

Record: `architecture:vector-clocks`
Kind: mechanism
Layer: [Causality Core](https://banes-lab.com/records/layer/causality-core.md)
Severity: contextual
Scope: distributed events, replication
Canonical: https://banes-lab.com/ontology#architecture-vector-clocks

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [Directed Acyclic Graph (DAG)](https://banes-lab.com/records/architecture/directed-acyclic-graph.md) and before [Lamport Clocks](https://banes-lab.com/records/architecture/lamport-clocks.md).

## Repair

- Refactored by: Add Version Vector
- Detected by: lost causality in distributed updates
- Violated by: unresolved concurrent writes
- Measured by: conflict detection accuracy
- Enforced by: replication protocol tests

## Requires

- [Node Identity](https://banes-lab.com/records/lexicon/node-identity.md)
- [Version Vector](https://banes-lab.com/records/lexicon/version-vector.md)

## Reinforces

- [Causal Consistency](https://banes-lab.com/records/architecture/causal-consistency.md)

## Enables

- [Concurrent Update Detection](https://banes-lab.com/records/lexicon/concurrent-update-detection.md)

## Conflicts with

- [Single Global Clock Assumption](https://banes-lab.com/records/lexicon/single-global-clock-assumption.md)

## In tension with

- [Metadata Size](https://banes-lab.com/records/lexicon/metadata-size.md)

## Tensions

- [Vector Clocks / Metadata Size](https://banes-lab.com/records/tension/metadata-size-vector-clocks.md)

## Severity

- [contextual](https://banes-lab.com/records/vocabulary/severity-contextual.md)

## Category

- [Causality / Ordering / Distributed Time](https://banes-lab.com/records/architecture-category/causality-ordering-distributed-time.md)

## Linked from

- [Execution joins the halves](https://banes-lab.com/software-architecture/principles/execution-joins-the-halves.md)
- [Causality / Ordering / Distributed Time](https://banes-lab.com/ontology/principles/architecture-category-causality-ordering-distributed-time.md)
- [Causality / Ordering / Distributed Time](https://banes-lab.com/ontology/lexicon/lexicon-category-causality-ordering-distributed-time.md)
- [Severity levels](https://banes-lab.com/ontology/schema/the-vocabulary-severity.md)
- [The resolutions](https://banes-lab.com/ontology/schema/the-resolutions.md)