1. A method of data processing in a data processing system having a processor core and a shared memory system including a cache memory that supports the processor core, the method comprising: receiving, at the cache memory, a transactional memory access request issued by the processor core in response to execution of a memory access instruction in a memory transaction undergoing a current execution by the processor core; dispatch logic of the cache memory evaluating the transactional memory access request for dispatch for servicing by the cache memory, wherein the evaluating includes determining whether the memory transaction has a failing transaction state; and in response to determining the memory transaction has a failing transaction state, the dispatch logic refraining from dispatching the memory access request for service by the cache memory during the current execution of the memory transaction and the cache memory refraining from updating at least replacement order information of the cache memory in response to the transactional memory access request during the current execution of the memory transaction.