Hi tsakumar81,
The DataType is specified as VARCHAR having length 3.
So when you pass characters more than 3, automatically it passed 3 characters by skipping all the others.
LEN function always returns 3 or less than 3. It never returns greater than 3.
So in order to validate you need to check the length from code behind and display the error message.
Once success, pass the value having 3 or less than 3 characters to the Stored procedure.