Glossary · System coordination, integration and orchestration
State replication
Also known as: Replication
German: Zustandsreplikation
In redundant and distributed systems, state replication is the continuous copying of a system's state, such as data, variables or process images, from one node to one or more other nodes, so that another node can take over or serve reads with the same state.
- System integration
In one sentence
State replication copies a system's state from one node to others so another node can take over or serve reads with the same state.
Example
In a redundant PLC pair, the primary controller replicates its process data to the standby every cycle, so the standby can take over without a restart.
How it applies
- Engineering: Replication can be synchronous (each change confirmed by the replica) or asynchronous (changes shipped later). Redundant controllers typically replicate synchronously within the cycle, databases often asynchronously.
- Operation: Monitor replication health. A standby that has silently stopped replicating gives false confidence in Redundancy.
- Change: Software or firmware updates on redundant systems must keep replication compatible, or updates require a planned shutdown.
- Documentation: Describe what is replicated, what is not (for example local diagnostic buffers), how long a switchover takes and what data can be lost. Operators and maintenance staff need these facts to trust and handle the system correctly.
State replication vs. state synchronization
State replication copies state from a primary to replicas in one direction. State synchronization is a broader term that includes keeping state consistent between peers, possibly in both directions and with conflict resolution.