To reset the password of the user you can use the Follwing Function module
CALL FUNCTION 'RSEC_GENERATE_PASSWORD'
alphabet = 'ABCDEFGHIJKLMNPQUVWXYZ123456789'
output_length = 12
output = Var_pass
some_error = 1
OTHERS = 2.
You will get the new generated password form the above Function.
After that pass your reset password and username to the below Function.
CALL FUNCTION 'BBPU_USER_CHANGE_ZBV'
username = pass_username
password = Var_pass
passwordx = 'X'
return = errors.
And after that you can send the user the mail with his new password.
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