eXtremeDB/rt

Deterministic ACID-compliant Transactions
Real-time vs. Non-real-time Database Systems
Like conventional database systems, real-time database systems are data repositories and provide services for storage, retrieval and manipulation of data. The differences between conventional and real-time database systems lie in the temporal requirements of the managed data, timing constraints on transactions, and performance goals. The following aspects are often considered:
a) internal versus external consistency constraints and,
b) transaction schedules and performance metrics.
The design principles of conventional (i.e., non-real-time) database systems always guarantee strong internal data consistency — a consistent view from all components of the database, avoiding contradictory data in the same database. To guarantee internal consistency, database systems ensure transactions’ ACIDAtomicity, Consistency, Isolation and Durability properties. Real-time database system designers sometimes argue that, for real-time databases, external consistency (the requirement for a transaction to reflect the current physical environment), is preferable. Indeed, external consistency may be more important than internal consistency for certain applications. However, as a practical matter, most applications require preserving their databases’ internal consistency.
Performance metrics
The common performance metric for all database systems is response time. For conventional database systems, the metric comes down to a number of transactions per time unit; this measurement – the average number of transactions per second (TPS) – is used heavily in optimizing the responsiveness of traditional database applications. In contrast, real-time database systems often use firm deadline semantics for transactions — transactions can “meet” (successfully commit) or “miss” (successfully abort) their deadlines, but cannot be “late” (go over their allotted time slot) to commit or abort their execution. A late commit of a real-time transaction can lead to a system’s state being incoherent. Thus, a typical performance metric for real-time databases is the number of transactions that miss their deadline.
eXtremeDB/rt implementation of deterministic ACID real-time transactions
eXtremeDB/rt provides semantics for passing a transaction’s deadline and priority to the database scheduler. Transactions are then scheduled either through the Earliest Deadline First (EDF) or Priority Inheritance (PI) algorithms (the schedule is serializable — “read-write” transactions are executed sequentially, “read-only” in parallel). Once scheduled, the eXtremeDB/rt transaction manager implementation enforces firm deadlines through utilizing a deterministic rollback policy. Data modifications or retrieval are allowed only if they are able to finish the within the transaction’s set deadline. “Late” transactions are identified, interrupted and forced to initiate rollback in time to satisfy set deadlines. The key is to ensure that all database runtime internals are in a “recoverable” condition. The database kernel reserves enough time out of the given transaction deadline to rollback modifications made to the point of interruption. We can prove that, at the control point, a transaction’s rollback time is less than the time the transaction has spent modifying the database, or searching through the database.
Learn more about eXtremeDB/rt
Related Resources
Documentation & Collateral
Review the eXtremeDB/rt data sheet
Learn more about eXtremeDB/rt in our on-line documentation
eXtremeDB/rt Q & A: what distinguishes a true real-time database?
In the News
"Embedded Databases in Real-Time Systems" CircuitCellar.com March 14, 2022 A Tech the Future article about the future of real-time computing

Tailored to your needs
The nature of eXtremeDB/rt’s tight integration with the RTOS and target hardware requires that each evaluation package be assembled uniquely for your needs.
Please contact us so that we can gather information on your RTOS vendor, version, target hardware, tool chain, and so on.
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Desktop distributions
Desktop evaluation packages of eXtremeDB/rt for Linux, MacOS, and Microsoft Windows platforms are available for free download. Learn more about the programming interface and various real-time and non-real-time features of eXtremeDB/rt. After you have tried the desktop version, we hope you’ll contact us for a free trial of eXtremeDB/rt tailored to the needs of your RTOS.
You are also welcome to contact us, and we will send you a download of eXtremeDB/rt running in the FreeRTOS simulator.
Articles about hard real-time data management and eXtremeDB/rt.


"Embedded Databases in Real-Time Systems"
CircuitCellar.com, March 14, 2022

"McObject and Siemens Embedded Announce Immediate Availability of eXtremeDB/rt for Nucleus RTOS"
ODBMS.org, February 23, 2022

"Embedded Executive: Steve Graves, President and CEO, McObject" EmbeddedComputing.com, January, 2022 An interview reviewing key concepts in real-time computing.

"Why your mission-critical application needs a real-time database management system", Logic.nl
January 4, 2022

"McObject Announces Availability of eXtremeDB/rt for Microsoft Azure RTOS ThreadX" Electronic Engineering Journal November 11, 2021

"McObject Collaborates with Wind River to Deliver the First-Ever Deterministic Database Systems for VxWorks-based Real-time Embedded Systems" COTS Journal, October, 2021 Please find us on page 8.

"Databases in Hard Real Time" McObject Launches True Real-Time Deterministic Database for embOS Real-time Operating System Applications, Wilmott.com,
October 15, 2021

"On eXtremeDB/rt. Q&A with Steven Graves, Real-time analytics has nothing to do with real-time systems." By Roberto Zicari ODBMS.org,
October 7, 2021.

"Keeping A Mission-Critical Deterministic DBMS On Time" by McObject CTO Andrei Gorine EmbeddedComputing.com,
September 20, 2021

"Real time tasks need real time data" Read the Wind River blog, September 7, 2021


"Embedded Databases in Real-Time Systems"
CircuitCellar.com, March 14, 2022

"McObject and Siemens Embedded Announce Immediate Availability of eXtremeDB/rt for Nucleus RTOS"
ODBMS.org, February 23, 2022

"Embedded Executive: Steve Graves, President and CEO, McObject" EmbeddedComputing.com, January, 2022 An interview reviewing key concepts in real-time computing.

"Why your mission-critical application needs a real-time database management system", Logic.nl
January 4, 2022

"McObject Announces Availability of eXtremeDB/rt for Microsoft Azure RTOS ThreadX" Electronic Engineering Journal November 11, 2021

"McObject Collaborates with Wind River to Deliver the First-Ever Deterministic Database Systems for VxWorks-based Real-time Embedded Systems" COTS Journal, October, 2021 Please find us on page 8.

"Databases in Hard Real Time" McObject Launches True Real-Time Deterministic Database for embOS Real-time Operating System Applications, Wilmott.com,
October 15, 2021

"On eXtremeDB/rt. Q&A with Steven Graves, Real-time analytics has nothing to do with real-time systems." By Roberto Zicari ODBMS.org,
October 7, 2021.

"Keeping A Mission-Critical Deterministic DBMS On Time" by McObject CTO Andrei Gorine EmbeddedComputing.com,
September 20, 2021

"Real time tasks need real time data" Read the Wind River blog, September 7, 2021