1. A computer-readable medium having computer-executable instructions for causing a computer to perform a method comprising: creating, within a shared software transactional memory, a plurality of closed nested transactions for a single parent transaction, wherein the closed nested transactions and the single parent transactions are software supported transaction; executing, within the shared software transactional memory, the closed nested transactions concurrently as parallel nested transactions, including; allowing, with software, effects of one of the parallel nested transactions to roll back if the one parallel nested transaction is discovered to be in conflict with some other concurrent transactions; and hiding effects of the parallel nested transactions from other transactions outside the parent transaction until the parent transaction commits in the shared software transactional memory.