What does 'Propagation.NEVER Executes non-transactionally' mean in Spring? - spring

Question

In the code below, the save operation in createDevice method inside DeviceService class will not be executed inside a transaction, what does it mean that this operation is not executed inside a transaction?
Is it possible to execute an operation on the database without a transaction?
package controller;
import model.Device;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.bind.annotation.RestController;
import service.DeviceService;
#RestController
public class DeviceController {
#Autowired
private DeviceService deviceService;
#PostMapping("/devices")
#ResponseStatus(HttpStatus.CREATED)
public void createDevice(#RequestBody Device device) {
deviceService.createDevice(device);
}
}
--
package service;
import model.Device;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;
import repository.DeviceRepository;
#Service
public class DeviceService {
#Autowired
private DeviceRepository deviceRepository;
#Transactional(propagation = Propagation.NEVER)
public void createDevice(Device device) {
deviceRepository.save(device);
}
}
--
package repository;
import model.Device;
import org.springframework.data.jpa.repository.JpaRepository;
public interface DeviceRepository extends JpaRepository<Device, Integer> {
}
--
package model;
import javax.persistence.Entity;
import javax.persistence.Id;
#Entity
public class Device {
#Id
private Integer id;
private String name;
}
Edit
I'm using MySQL database.
The Operation gets executed successfully.
Any details on how this gets executed without a transaction? What is being done behinde the scene?
What is the difference between executing an operation inside a transaction and without a transaction?