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Real-time Deterministic Database Management

From the real-time database management system experts at McObject

A summary of the white paper by McObject, “Real-time Deterministic Database Management?” about the objectives of deterministic, predictable database management in the context of real-time application design.

Abstract—This paper will discuss the objectives of deterministic, predictable database management in the context of real-time application design. We will introduce extensions to a conventional database management systems (DBMS) transaction scheduler that add semantics, enforce database transaction priorities and deadline scheduling. We will then focus on the practical aspects of the design and demonstrate its use in several real-life application patterns in a variety of real-time operating system (RTOS) environments.

“The differences between conventional and real-time databases lie in the temporal requirements of the managed data, timing constraints on transactions, and performance goals.”

The Need for a Deterministic Real-time Database Management System

Embedded devices and software have been a staple of modern life for decades. Long gone are the times when the majority of embedded software was created from scratch. The “build vs. buy” alternative is no longer debated — commercial off-the-shelf (COTS) embedded operating systems, database management systems and other middleware and tools are routinely utilized in almost all areas of embedded systems’ development. Moreover, the last decade has seen commercial software making its way into product designs that have always been considered “out-of-reach” of commercial software vendors — avionics, autonomous systems, critical control systems, and the like. These applications’ missions are often non-interruptible and impose stringent requirements on their timely execution. These requirements are often defined as real-time constraints on the systems’ temporal behavior. For example, an action performed too late or a computation that used temporary inconsistent data can be useless or harmful even if those actions or computations are functionally correct. Mission- and safety-critical systems’ manufacturers have recognized that using specialized real-time operating systems and components to fulfill critical-path functionality requirements improves the systems’ stability and reduces time to market. Real-time database management systems that preserve the temporal validity of data through time-cognizant transaction processing that guarantees predictable execution of critical transactions needs to be developed and made available commercially.

"In other words, it’s easy to add ingredients to your pie (CPU cycles and memory consumption). But once they’re in the pie mix, you can’t really take those ingredients out, short of a rewrite."

Learn more about eXtremeDB/rt

eXtremeDB/rt is the first commercial-off-the-shelf (COTS) embedded database system to enforce database transaction deadlines, making it uniquely suitable for embedded systems with hard real-time constraints. As an ACID-compliant DBMS, eXtremeDB/rt guarantees internal consistency, but with real-time features also guarantees external consistency when transactions complete within their deadline.

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Deterministic ACID-compliant transactions

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Adaptable real-time transaction managers

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No restrictions on execution patterns

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Highly configurable database kernel

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The eXtremeDB reliable in-memory database system is found in systems that cannot afford to fail