JPA for WebSphere Application Server is built on the Apache OpenJPA open source project.
Apache OpenJPA and JPA for WebSphere Application Server
Apache OpenJPA is a compliant implementation of the Sun Microsystems JPA specification. Using OpenJPA as a base specification, WebSphere Application Server employs extensions to provide additional features and utilities for WebSphere Application Server customers. Because JPA for WebSphere Application Server is built from OpenJPA, all OpenJPA functionality, extensions and configurations are unaffected by the WebSphere Application Server extensions. Users running OpenJPA applications do not need to make any changes to use their applications in WebSphere Application Server.
JPA for WebSphere Application Server provides more than compatibility with OpenJPA. JPA for WebSphere Application Server contains a set of tools for application development and deployment. In addition, JPA for WebSphere Application Server allows users to plug in alternate persistence providers. Other features of JPA for WebSphere Application Server include the ability to batch their SQL statements together to achieve better performance, support for XML mapping, and translated message files.
The Extension Properties of JPA for WebSphere Application Server may be specified with the openjpa or wsjpa prefix. You can mix the openjpa and wsjpa prefixes as you wish for a common set of properties. Exceptions to the rule are wsjpa specific configuration properties, which should use the wsjpa prefix only. In the event that a JPA for WebSphere Application Server specific property is used with the openjpa prefix, a warning message will be logged indicating that the offending property will be treated as a wsjpa property. The reverse does not hold true for the openjpa prefix. In that case the offending property will merely be ignored.