I have set of detail records.

When i delete master, then details also deleted as well.

But i cannot delete just details. Tryed clear collection, but it doesn't work.
How i can do that?

Is that about cascade="all-delete-orphans"?

If you want to keep the parent, but delete the children, you would probably have to iterate through the set of children and delete each one by itself. I'm not sure you can do this: session.delete(parent.getChildren())

-G

correct, and you must call remove on your set passing the object you want to remove, I quickly squizzed at removeAll, which takes another collection, maybe try passing the collection you have, you'll get back a boolean.
then just save your parent object.