There is problem, when parent entity has generated value IDENTITY and batch update is enabled.

This happens only (if all conditions are met):

• parent has generated value IDENTITY (changing this to SEQUENCE fixes problem)
• if parent entity has child list initialized on class instantialization
  and one parent is read from database, and the other is created in session and flushed
  than two child entities are created for each, and linked and flushed .
• persisence factory property 'hibernate.order_updates' is set to true

LOG OF EXCEPTION

Error output of class: java.lang.ClassCastException:449895102
org.hibernate.action.internal.DelayedPostInsertIdentifier cannot be cast to java.lang.Long
Stack:
java.lang.Long.compareTo(Long.java:54)
org.hibernate.internal.util.compare.ComparableComparator.compare(ComparableComparator.java:23)
org.hibernate.internal.util.compare.ComparableComparator.compare(ComparableComparator.java:18)
org.hibernate.type.AbstractStandardBasicType.compare(AbstractStandardBasicType.java:215)
org.hibernate.action.internal.CollectionAction.compareTo(CollectionAction.java:159)
org.hibernate.engine.spi.ExecutableList.add(ExecutableList.java:227)
org.hibernate.engine.spi.ActionQueue.addAction(ActionQueue.java:307)
org.hibernate.engine.spi.ActionQueue.addAction(ActionQueue.java:371)
org.hibernate.event.internal.AbstractFlushingEventListener.flushCollections(AbstractFlushingEventListener.java:301)
org.hibernate.event.internal.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:95)
org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:38)
org.hibernate.internal.SessionImpl.doFlush(SessionImpl.java:1454)
org.hibernate.internal.SessionImpl.flush(SessionImpl.java:1440)

created data model for DB2 and testCase ORM5 are included in:
[^DB2_MODEL.txt]
[^TestVersion_ORM5_Without_db2_project related data.zip]