As I wrote in a different posting, I had a problem that Session.Flush took 11 sec, just to save one object, because I had 11.000 objects in memory. All my attempts to speed that up failed. I see the following possibilities (and their problems) for my problem:

1.) One big session for the app. Everytime I need data, I reconnect and get them from DB, everytime I save data, I reconnect and save to DB. That's what I do now, with the problem, that with many objects it is very slow at flushing.

2.) One big session to get all data, and a second small one, which I always clear and associate only the objects I want to save before updating just the data I want to save. PROBLEM: I get the following exception: "Illegal attempt to associate a collection with two open sessions"

3.) One session, which I always clear before saving and just associate with Lock the object(s) I want to save. There I have two problems: PROBLEM 1: When trying to associate I get the exception: reassociated object has dirty collection reference. And PROBLEM 2: After I clearing the session, it can happen that (because of a reference) a object is reloaded from the DB, which I already loaded, as a seperate object in memory (because the first one is not longer in the session). So I have two identical representations of the same object.

I hope you understand my problem. the question is, what is the best practice to solve my problem, which is a standard usage scenario for NHibernate.

Thanks alot, Rainer.

Have you read: How to handle session in winforms?

You should never use one big session for the entire application. Sessions should be small and relatively short-lived and correspond to some kind of transaction, so that you can rollback and throw away the whole session in case something goes wrong.

Regarding your option 3), can you just start a new session and call session.SaveOrUpdate(myNewOrChangedObject)?

Thanks for the link to the other thread. I will write there.