Overview
Data Consistency is a core principle of database reliability (the 'C' in ACID). It ensures that data remains valid according to all defined rules, including constraints, cascades, and triggers. In distributed systems, consistency also refers to whether all nodes in a cluster see the same data at the same time.
Consistency Models
- Strong Consistency: After an update, all subsequent accesses will return the updated value.
- Eventual Consistency: Given enough time without further updates, all accesses will eventually return the last updated value (common in NoSQL).
- Causal Consistency: Ensures that operations that are causally related are seen in the same order by all observers.
Importance
Consistency is vital for financial transactions, inventory management, and any application where accuracy is paramount.