Memory system and operation method thereof

An operation method of a memory system which comprises a nonvolatile memory including a plurality of blocks each having a plurality of pages, a volatile memory for temporarily storing data transferred between a host and the nonvolatile memory, and a command queue for storing a plurality of commands transferred from the host, the operation method comprising:

• repeatedly entering and exiting from an automatic exclusive mode for each predetermined size of write data which are transferred from the host and written to the nonvolatile memory, in a start period of the automatic exclusive mode;
• exclusively using the volatile memory to perform a merge operation on the nonvolatile memory during an entry period of the automatic exclusive mode;
• and
• calculating a processing time of write commands among the commands stored in the command queue and an entry time of the entry period of the automatic exclusive mode, using a preset operation in the start period of the automatic exclusive mode, and then scheduling a processing order of the commands stored in the command queue according to the calculation result.