SQL & PL/SQL

I wrote the follwing procedure:
PROCEDURE pColuna
(e_owner IN VARCHAR2,
e_nmTab IN VARCHAR2,
e_nmCol IN VARCHAR2,
s_deTip OUT VARCHAR2,
s_nuTam OUT VARCHAR2)
IS
v_data_length VARCHAR2(30);
v_data_precision VARCHAR2(30);
s_demsgrerro varchar2(1000);
BEGIN
SELECT DATA_TYPE, DATA_LENGTH, DATA_PRECISION
INTO s_deTip, v_data_length, v_data_precision
FROM ALL_TAB_COLUMNS
WHERE OWNER = e_owner
AND TABLE_NAME = e_nmTab
AND COLUMN_NAME = e_nmCol;

IF s_deTip = 'VARCHAR2' THEN
s_nuTam := v_data_length;
ELSE
s_nuTam := v_data_precision;
END IF;
EXCEPTION
WHEN NO_DATA_FOUND THEN
s_deTip := 'VARCHAR2';
s_nuTam := 10;
END;

For all values passed, the exception NO_DATA_FOUND is raised, even when the row exists in the view.

What can I do?

Tks in advance.