DATALENGTH - Returns the number of bytes used to represent any expression.
LEN - Returns the number of characters of the specified string expression, excluding trailing blanks
Output is 30, 3.
Important point to remember is is LEN function does not depend on the data type and it is storage mechanism. LEN function total depends on the number of string characters.
Output is 8 and 3.
So DATALENGTH is depends on the storage but not the LEN function.