1. A method, comprising: in a multiprocessor data processing system having a distributed shared memory system, executing a first memory transaction that is a rewind-only transaction (ROT) including one or more transactional memory access instructions, a transactional abort instruction, and a transaction-ending instruction that delimits an end of the ROT; in response to execution of the one or more transactional memory access instructions, performing one or more memory accesses to the distributed shared memory system indicated by the one or more transactional memory access instructions; in response to execution of the transactional abort instruction prior to execution of the ROT reaching the transaction-ending instruction, unconditionally discarding execution results of the one or more transaction memory access instructions and passing control to a fail handler; in the multiprocessor data processing system, executing a second memory transaction that is a non-rewind-only transaction and, during execution of the second memory transaction, tracking conflicts between both load and store footprints of the second memory transaction and memory accesses not within the second memory transaction; and during execution of the first memory transaction, refraining from tracking conflicts between a load footprint of the first memory transaction and memory accesses not within the first memory transaction.