1. A method of controlling a coalescing of outermost memory transactions, the coalescing causing committing of memory store data to memory for a first transaction to be done at transaction execution (TX) end of a second transaction, the method comprising: executing, by a processor, a run-time instrumentation program for monitoring and modifying an associated program having a plurality of transactions; initiating, by the processor, execution of the associated program; based on execution of transactions, by the processor, of the associated program, the run-time instrumentation program dynamically obtaining instrumentation information associated with the execution; and based on the obtained instrumentation information, dynamically modifying, by the processor, continued execution of transactions of the associated program to optimize transactional execution (TX).