Abstract: According to one embodiment, in a memory system, the overlap checker is configured to perform a preliminary check operation that checks whether or not there is a logical address overlap between a first command and a second command. The first command is received by the host interface. The second command is received prior to the first command. The second command is an uncompleted command. The overlap checker is configured to queue a command received by the host interface in the command queue, and perform a recheck operation that checks whether or not there is a logical address overlap between a third command and a fourth command. The fourth command is received prior the third command. The fourth command is an uncompleted command. The third command includes an overlapped logical address detected by the preliminary check operation. The third command is dequeued by the command execution processing unit.