This is a rough rendering of a page from the old Prevayler wiki. Please see the new wiki for current documentation.

Prevayler is the most reliable FreeSoftware Prevalence layer we are capable of providing for Java.

Prevalence is by far the fastest, simplest and most transparent business object persistence, ACID transaction, fault-tolerance, replication and load-balancing architecture we know.


Queries with Prevayler are more than 9000 times faster than querying Oracle through JDBC.
Queries with Prevayler are more than 3000 times faster than querying MySQL through JDBC.
(Even with the Oracle and MySQL databases fully cached in RAM and on the same physical machine as the test VM. @:o See ScalabilityTestResults)


With Prevalence we are finally free to create true object servers and use objects the way they were intended all along.

We are able to use any algorithm, data-structure and query language we please. We are no longer constrained to the ones provided by database and application servers which must run on disk data-blocks.
(See HowDoIQueryMyObjects? WhatAreTheCodingRestrictions?)

We believe the whole OO community is finally free to recover from the atrophy caused by database and application server restraints. We no longer have to distort and maim our object models to satisfy their limitations.

We no longer have DBAs imposing us database layout restrictions. We have freed them to do something more useful.

We have set fire to the table-models on our walls. We have deleted our database creation scripts. We no longer have to keep them updated.

We no longer have to license, install, configure and maintain a database and application server every single time we want to develop, demonstrate or deploy our systems for any of our clients. Give us a Java VM and we are good to go. @:)


Prevalence requires us to have enough RAM on our servers to contain all our business objects. We have found that to be the case already in many of the systems we are deploying. With the steady evolution in RAM technology, we believe that this will also be true for the vast majority of systems in the near future. (See BreakthroughsInMemoryTechnology)


The simple concepts behind prevalence have been around for ages. To use Prevayler, though, we have faced fear and resistence from our peers, bosses and clients.

We use Prevayler not because it is the easiest alternative to justify, but because we believe it is the best. @8)


To learn more about Prevayler and Object Prevalence, take a look at GettingStarted.

If you can provide a more reliable implementation of a prevalence layer or, if you can describe a more transparent, faster or simpler architecture than prevalence, please let us know: BetterAlternativesToPrevayler.

To sign the Prevalent Manifesto above, just append your name and we'll add it to the list: