No idea what the history behind this is (it almost looks like someone misinterpreted the JPA query hint of the same name and turned it into a session-level config property by accident), but:

• org.hibernate.flushMode does not satisfy our naming convention for config properties,
• it’s undocumented, and
• I don’t see how it’s useful.

Let’s deprecate it, and if anyone screams out, we can consider adding a property that does obey the usual naming convention.