After our meeting, Patrick did some analysis of our current API and where we might want to take it. Here are some initial observations. Please comment as appropriate.

• OpenJPAEntityManager extends EntityTransaction; should it?
  clr no, I like your idea below to add an OpenJPAEntityTransaction interface, so users could do OpenJPAEntityTransaction tx = (OpenJPAEntityTransaction)em.getTransaction();

• StoreCache, QueryResultCache, Extent, FetchPlan, Generator, OpenJPAQuery all have getDelegate() calls that return an underlying kernel implementation detail. Maybe these should be pushed down to theh impl classes only?
  clr I agree these don't belong in OpenJPAEntityManager

• OpenJPAEntityManager and OpenJPAEntityManagerFactory both have a getConfiguration() method. Maybe this should be pushed down to the impl classes only?
  clr I don't know when I would use the Configuration, so no opinion on this one.

• OpenJPAEntityManager.getManagedRuntime() should be pushed down to impl only
  clr I agree

• The following methods in OpenJPAPersistence return things that are not currently part of what I consider a user-focused API:
  toBrokerFactory()
  toBroker()
  toEntityManagerFactory()
  toEntityManager()
  getMetaData()
  toOpenJPAObjectId() / toOpenJPAObjectIds()
  
  I think that we should move these methods to o.a.o.persistence.impl.ImplHelper or some other impl-specific class.
  
  clr I agree.

• We have a bunch of methods in OpenJPAEntityManager that seem like they should belong on a new OpenJPAEntityTransaction interface:
  public void commitAndResume();
  public void rollbackAndResume();
  public void setRollbackOnly(); (already part of EntityTransaction)
  public void setRollbackOnly(Throwable cause);
  public Throwable getRollbackCause();
  public boolean getRollbackOnly(); (also already part of EntityTransaction)
  
  public boolean isStoreActive();
  public void beginStore();
  
  I'm not quite as sure where these belong:
  
  public void setSavepoint(String name);
  public void rollbackToSavepoint();
  public void rollbackToSavepoint(String name);
  public void releaseSavepoint();
  public void releaseSavepoint(String name);
  
  public void preFlush();
  public void validateChanges();
  
  clr All of these seem like transaction-focused methods that belong in OpenJPAEntityTransaction...
  pcl: I moved the commit / rollback / rollbackOnly stuff into OpenJPAEntityTransaction, but things are trickier for the rest of the methods: you can only call EM.getTransaction() when not in a JTA context, and these other methods are valuable in a JTA env as well as a non-JTA env. So, we can either leave them on OpenJPAEM or create some other interface for them.

• I don't like the OpenJPAEntityManager.setLargeTransaction() method name - I'd like to rename it to setTrackChangesByType() instead, since it better reflects what the method does. (We can easily deprecate the old method if desired.)
  clr I kinda like setLargeTransaction. It's more "task-oriented".
  pcl: The thing is that if you are using large transactions, you might want to call either (or both) setLargeTx() and setPopulateDataCache(), depending on the nature of the tx workload.

• I think that it might make sense to move OpenJPAEntityManager.setPopulateDataCache() to FetchPlan, and rename FetchPlan.setQueryResultCache() to setPopulateQueryResultCache(). (We can easily deprecate the old methods if desired.)
  clr No opinion here.