Clarifying a couple of my earlier comments...
The use of non-jta-data-sources in WebSphere will allow the use of DB2 Sequences. This support does not require the ability to suspend the current transaction. But, it would still be nice to have the ability to access database sequences without requiring the use of non-jta-data-sources. This transaction suspension can be done via WebSphere's UOWSynchronizationRegistery API. We should use this JIRA Issue to track this additional "feature". In the mean time, WebSphere users should use the spec-compliant non-jta-data-source element.
Through discussions with Patrick, he has indicated a desire to make this support more general so that it could apply to other environments more easily. He has opened
OPENJPA-159 for this purpose. Thus, these two Issues ( OPENJPA-159 and OPENJPA-149) are very much related.
Just wanted to clarify my earlier comments and what the differences are between 149 and 155.