MEMORY SYSTEM, MEMORY CONTROLLER FOR MEMORY SYSTEM, OPERATION METHOD OF MEMORY CONTROLLER, AND OPERATION METHOD OF USER DEVICE INCLUDING MEMORY DEVICE

A system includes: a nonvolatile memory; a memory controller configured to control the nonvolatile memory, the memory controller including a first buffer memory for temporarily storing write data to be written to the nonvolatile memory; and a second buffer memory having a lower operational speed and a higher memory capacity than the first buffer memory. The memory controller is configured to transmit the write data from the first buffer memory to the second buffer memory and to the nonvolatile memory, and to release an operational state of the first buffer memory after transmitting the write data from the first buffer memory to the second buffer memory and to the nonvolatile memory. Writing additional write data to the first buffer memory is prohibited prior to the release of the operational state of the first buffer memory, and is permitted after the release of the operational state of the first buffer memory.