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## Availability and Failover

Oracle NoSQL Database is a data storage product with enormous scalability and performance benefits. Additionally, Oracle NoSQL Database offers excellent availability mechanisms. These mechanisms are designed to provide your applications access to data contained in the store in the event of localized hardware and network failures.

This document describes the mechanisms Oracle NoSQL Database uses to ensure your data remains available, along with the various failover algorithms that Oracle NoSQL Database employs. In addition, this document describes application design patterns you can use to best make use of Oracle NoSQL Database's availability mechanisms. In some cases, tradeoffs exist between ensuring data is highly available, and achieving optimal performance. This document explores these tradeoffs.

The intended audience for this document includes system architects, engineers, and others who want to understand the concepts and issues surrounding data availability when using Oracle NoSQL Database. In addition, software engineers responsible for writing code that interacts with an Oracle NoSQL Database store should also read this document.

We recommend that you read and get familiar with the following contents before continuing.

- Developers Guide

  This document introduces terms and concepts you need to know before reading this document.

- Durability Guarantees in the Java Direct Driver Developer's Guide

  This section includes concepts that lead to issues surrounding write availability.

- Consistency Guarantees in the Java Direct Driver Developer's Guide

  This section includes concepts that lead to issues surrounding read availability.