1, a total of two environment variables, one in Flash and the other in the DDR. uboot boot-time read from the Flash to all environmental variables to initial values as the DDR environment variable, and process of using it are made of a DDR, the user may use the instruction saveenv DDR environment variables rewriting Flash in Flash to update the environment variables. The next one will read from Flash boot.
2, the environment variable is represented by the string in uboot, ie uboot a manner matching character to distinguish respective environment variables. So when we must pay attention not to use the wrong word.