Radim Vansa I am in the process of incorporating this discussion into the 6.0 branch and am trying to include you proposal regarding CacheTransactionContext
(renamed from CacheSynchronization) but I needed to clarify your exact expectations about its relation to Session in terms of "multiple transactions" against a single Session. Assuming that Session exposed this context (it won't, but for the purpose of illustration for this discussion...), what do you expect below in regards to the assertions?

TransactionManager tm = ...;
SessionImplementor s = ...;

tm.beginTransaction();
CacheTransactionContext ctc1 = s.getCacheTransactionContext();
tm.commit();

tm.beginTransaction();
CacheTransactionContext ctc2 = s.getCacheTransactionContext();
tm.commit();

assert ctc1 == ctc2;
assert ctc1.getSession().getTransactionStartTimestamp() == ctc2.getSession().getTransactionStartTimestamp();
...