When running in a cluster, jBPM synchronizes on the database. By default with optimistic locking. This means that each operation is performed in a transaction. And if at the end a collision is detected, then the transaction is rolled back and has to be handled. E.g. by a retry. So optimistic locking exceptions are usually part of the normal operation. Therefor, by default, the org.hibernate.StateObjectStateExceptions the that hibernate throws in that case are not logged with error and a stack trace, but instead a simple info message 'optimistic locking failed' is displayed.

Hibernate itself will log the StateObjectStateException including a stack trace. If you want to get rid of these stack traces, put the level of org.hibernate.event.def.AbstractFlushingEventListener to FATAL. If you use log4j following line of configuration can be used for that:

log4j.logger.org.hibernate.event.def.AbstractFlushingEventListener=FATAL

If you want to enable logging of the jBPM stack traces, add the following line to your jbpm.cfg.xml:

<boolean name="jbpm.hide.stale.object.exceptions" value="false" />

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