1. A memory control apparatus which controls access to a shared memory for each transaction, the memory control apparatus comprising: a management unit that stores versions of data stored in the shared memory; a log storage unit that stores an update entry, including a version of data subjected to the update operation for the transaction, in response to execution of an update operation on the shared memory in processing of each transaction; and a control unit which when a request to commit a transaction has been given (i) writes a result of processing corresponding to execution of a relevant update operation to the shared memory if a version included in a relevant update entry matches a corresponding version of the versions stored in the management unit, and (ii) re-executes the update operation on the shared memory and writes a result of re-execution to the shared memory if the version included in the update entry does not match the corresponding version stored in the management unit.